explain xkcd - User contributions [en]

3124: Grounded

2025-08-06T10:34:31Z

2A02:AA10:EA7E:ED00:8544:4991:D1AC:AD5A: /* Explanation */

{{comic
| number = 3124
| date = August 4, 2025
| title = Grounded
| image = grounded_2x.png
| imagesize = 294x335px
| noexpand = true
| titletext = We should have you at the gate in just under two hours--two and a half if we get pulled over.
}}

==Explanation==
{{incomplete|This page was created recently by a COP ASKING IF THE PILOT KNOWS WHY THEY WERE PULLED OVER. Don't remove this notice too soon.}}

This comic depicts a plane that has been delayed due to unfavorable weather. The pilot and first officer have considered simply "driving" the plane to the destination instead of waiting for the weather report to clear up, announcing that they have considered their maximum taxiing speed and bridge clearance heights. Jetliners taxi at 25-35 mph — slower than a car or bus on a highway — and rolling at nearer to {{w|Rotation (aeronautics)|rotation}} speed for prolonged periods would be mechanically problematic, especially on non-straight roads. However, it is not necessarily illegal to drive slower than a posted speed limit, if it's done with safety in mind. Ordinarily, "driving" a commercial aircraft on a public highway could not be accomplished legally in the state of Massachusetts, where Randall Munroe lives, because vehicles being operated in Massachusetts [http://www.mass.gov/register-and-title-your-vehicle must be registered with the Massachusetts Registry of Motor Vehicles], while civil aircraft in the United States, as a matter of policy and regulations, would be solely registered [http://www.faa.gov/licenses_certificates/aircraft_certification/aircraft_registry by the Federal Aviation Administration]. It would be difficult or impossible to qualify an aircraft for federal emissions standards and other safety regulations, such as brake lights and visibility. "Driving" a plane according to this plan has traditionally been considered impractical, due to the excessive width and height (and maybe length) of the vehicle, and the {{w|Jet blast|backwash from the engines}}. Delays in air travel are known for creating desperate situations, which could lead the flight crew, and even passengers, to fantasize about resorting to these desperate measures.

Another consideration in driving an airliner long distance is brake overheating. Though carbon brakes have replaced the more problematic steel brakes a long time ago, aircraft brakes typically overheat during long taxiing. Also, engines are most efficient during cruise flight at cruise altitude, and least efficient when taxiing. Aircraft have run out of fuel during taxing, either after landing, or before take-off, through eating into the minimal fuel reserves. Through jet engines can burn a range of fuels ({{w|Jet A1}} is very loosely specified regarding its organic constituents, and refueling turbine-powered helicopters with unleaded automotive gasoline is an approved emergency procedure for many types), higher costs will be incurred through shorter inspection intervals and higher maintenance costs if the crew elects to refuel at highway gas stations.

The title text intensifies the humor, saying that driving will probably result in a traffic enforcement stop, and further extend the travel time. The "drive time" would probably be extended by more than 30 minutes, especially if the flight crew is required to stop, or disembark from the aircraft, or they could be prevented entirely from continuing onward.

===Motives and feasibility===

A number of factors contribute to the dilemma and increase the switching cost of using traditional ground transportation:

* If the plane continues to wait, it may need to do so for several hours.
* Allowing passengers to leave a sealed plane is typically a long process and may (depending on the situation and airport) involve the cancellation of the flight (which airlines are financially incentivized to avoid) or the plane losing its place in the increasingly long line of flights waiting to depart.
* Passengers often have checked luggage that takes a long time to unload and be delivered (a notoriously slow process).
* When a full flight's worth of passengers suddenly need ground transportation to the same place, there is sometimes not enough ground transportation readily available to transport them and their luggage.
* Passengers arriving at another airport via ground transportation and wishing to board a connecting flight would need to pass through security checkpoints and hand over their luggage again, further delaying the process.

The plane appears to have 14 passenger windows on one side, a moderate number associated with a narrow-body / single-aisle aircraft (likely with 4 seats per row - up to 56 passengers and around 4 crew). A plane of this size is more likely to fit on a wide road or under any overpass built for large trucks, compared to a large airliner with possibly hundreds of passengers. Smaller planes are also more commonly used for local flights with fewer passengers. It is possible that the destination is only 70 miles away by road (likely a nearby city of at least moderate size or else the plane would be smaller). Roads around airports are often crowded, but the poor weather may have reduced traffic to and from the airport, or the pilots may be counting on smaller vehicles staying out of their way. If the public roads are viable and local law enforcement does not interfere (or allows the plane to proceed due to jurisdictional confusion), then the largest practical obstacles may be exiting the first airport and entering the second. Large airports restrict access to the tarmac, and since the pilots intend to respect air traffic control's decision to prohibit flight, they would either need several people on the ground to open major gates, or would need to ram at least one sufficiently weak gate or fence at each end.

==Transcript==
:[A plane is at an airport gate, connected to the jet bridge going into an extensive building with many dark windows facing out towards the plane. There are several other ground vehicles nearby, one towing two empty wagons for luggage, and related equipment that includes several small traffic cones placed strategically around the plane. In the space behind the plane there is another, unoccupied, gate with a jet bridge extending from the building.]
:[A voice emanates from the plane, with a speech line starting at a star burst on top of the plane's cabin. The voice makes it clear that this is the captain speaking through the internal public address system:]
:Captain's voice: This is your captain speaking. As you've probably noticed, we're still grounded due to weather
:Captain's voice: But the first officer and I have been looking at bridge clearance maps and our top taxiing speed, and we have an idea.

{{comic discussion}}<noinclude>

[[Category:Aviation]]

3124: Grounded

2025-08-06T10:21:22Z

2A02:AA10:EA7E:ED00:8544:4991:D1AC:AD5A: /* Explanation */

{{comic
| number = 3124
| date = August 4, 2025
| title = Grounded
| image = grounded_2x.png
| imagesize = 294x335px
| noexpand = true
| titletext = We should have you at the gate in just under two hours--two and a half if we get pulled over.
}}

==Explanation==
{{incomplete|This page was created recently by a COP ASKING IF THE PILOT KNOWS WHY THEY WERE PULLED OVER. Don't remove this notice too soon.}}

This comic depicts a plane that has been delayed due to unfavorable weather. The pilot and first officer have considered simply "driving" the plane to the destination instead of waiting for the weather report to clear up, announcing that they have considered their maximum taxiing speed and bridge clearance heights. Jetliners taxi at 25-35 mph — slower than a car or bus on a highway — and rolling at nearer to {{w|Rotation (aeronautics)|rotation}} speed for prolonged periods would be mechanically problematic, especially on non-straight roads. However, it is not necessarily illegal to drive slower than a posted speed limit, if it's done with safety in mind. Ordinarily, "driving" a commercial aircraft on a public highway could not be accomplished legally in the state of Massachusetts, where Randall Munroe lives, because vehicles being operated in Massachusetts [http://www.mass.gov/register-and-title-your-vehicle must be registered with the Massachusetts Registry of Motor Vehicles], while civil aircraft in the United States, as a matter of policy and regulations, would be solely registered [http://www.faa.gov/licenses_certificates/aircraft_certification/aircraft_registry by the Federal Aviation Administration]. It would be difficult or impossible to qualify an aircraft for federal emissions standards and other safety regulations, such as brake lights and visibility. "Driving" a plane according to this plan has traditionally been considered impractical, due to the excessive width and height (and maybe length) of the vehicle, and the {{w|Jet blast|backwash from the engines}}. Delays in air travel are known for creating desperate situations, which could lead the flight crew, and even passengers, to fantasize about resorting to these desperate measures.

Another consideration in driving an airliner long distance is brake overheating. Though carbon brakes have replaced the more problematic steel brakes a long time ago, aircraft brakes typically overheat during long taxiing.

The title text intensifies the humor, saying that driving will probably result in a traffic enforcement stop, and further extend the travel time. The "drive time" would probably be extended by more than 30 minutes, especially if the flight crew is required to stop, or disembark from the aircraft, or they could be prevented entirely from continuing onward.

===Motives and feasibility===

A number of factors contribute to the dilemma and increase the switching cost of using traditional ground transportation:

* If the plane continues to wait, it may need to do so for several hours.
* Allowing passengers to leave a sealed plane is typically a long process and may (depending on the situation and airport) involve the cancellation of the flight (which airlines are financially incentivized to avoid) or the plane losing its place in the increasingly long line of flights waiting to depart.
* Passengers often have checked luggage that takes a long time to unload and be delivered (a notoriously slow process).
* When a full flight's worth of passengers suddenly need ground transportation to the same place, there is sometimes not enough ground transportation readily available to transport them and their luggage.
* Passengers arriving at another airport via ground transportation and wishing to board a connecting flight would need to pass through security checkpoints and hand over their luggage again, further delaying the process.

The plane appears to have 14 passenger windows on one side, a moderate number associated with a narrow-body / single-aisle aircraft (likely with 4 seats per row - up to 56 passengers and around 4 crew). A plane of this size is more likely to fit on a wide road or under any overpass built for large trucks, compared to a large airliner with possibly hundreds of passengers. Smaller planes are also more commonly used for local flights with fewer passengers. It is possible that the destination is only 70 miles away by road (likely a nearby city of at least moderate size or else the plane would be smaller). Roads around airports are often crowded, but the poor weather may have reduced traffic to and from the airport, or the pilots may be counting on smaller vehicles staying out of their way. If the public roads are viable and local law enforcement does not interfere (or allows the plane to proceed due to jurisdictional confusion), then the largest practical obstacles may be exiting the first airport and entering the second. Large airports restrict access to the tarmac, and since the pilots intend to respect air traffic control's decision to prohibit flight, they would either need several people on the ground to open major gates, or would need to ram at least one sufficiently weak gate or fence at each end.

==Transcript==
:[A plane is at an airport gate, connected to the jet bridge going into an extensive building with many dark windows facing out towards the plane. There are several other ground vehicles nearby, one towing two empty wagons for luggage, and related equipment that includes several small traffic cones placed strategically around the plane. In the space behind the plane there is another, unoccupied, gate with a jet bridge extending from the building.]
:[A voice emanates from the plane, with a speech line starting at a star burst on top of the plane's cabin. The voice makes it clear that this is the captain speaking through the internal public address system:]
:Captain's voice: This is your captain speaking. As you've probably noticed, we're still grounded due to weather
:Captain's voice: But the first officer and I have been looking at bridge clearance maps and our top taxiing speed, and we have an idea.

{{comic discussion}}<noinclude>

[[Category:Aviation]]