Can a delayed flight make up time in the air? And why the flight back is shorter

Sometimes. It depends less on flying faster than on three things: tailwinds, a shorter taxi or route than planned, and schedules with some extra time built in. What doesn't help is a delay imposed by air traffic control, because it holds planes to protect the destination airport.

Why the flight back can be shorter

Jet streams are narrow bands of strong wind high in the atmosphere, around 30,000 feet, that generally blow from west to east. Airliners cruise at about that height. NOAA explains that a plane flying with a powerful jet stream gets a boost, so a west-to-east flight can generally make the trip faster than the same route east to west.

• Stronger in winter. Jet streams are strongest in winter and can exceed 275 mph.
• They move. In summer the polar jet over North America is typically near the US–Canada border, and its position changes day to day.
• Routes follow them. Across the North Atlantic, eastbound and westbound flights use different daily track systems, because the fastest routes in each direction are rarely the same. See why planes fly curved routes.

So an eastbound flight that leaves late may regain part of the delay with a strong tailwind, while a westbound flight into a headwind has less room.

Schedules often include a buffer

A scheduled flight time isn't just time in the air. It's gate to gate: pushback, taxi-out, the flight, taxi-in and parking. Airlines set it knowing how long taxiing and congestion usually take at those airports. A 2000 report by DOT's Inspector General found that between 1988 and 1999, major US airlines lengthened scheduled flight times on over 80% of their domestic routes, and that between 1995 and 1999, 82% of the growth in gate-to-gate times came from longer taxi times rather than time in the air.

That means that on a day with short taxis and a direct routing, a flight can use less than its scheduled time and arrive closer to on time than its late departure suggested. For US statistics, arriving at the gate less than 15 minutes late counts as on time.

When a delay can't be made up

• Ground delay programs and ground stops. When the destination airport can't take more arrivals, the FAA holds flights at their departure airports and assigns a wheels-off time. The delay exists because the destination is full, so the flight won't recover it on the way. See ground stop vs. ground delay.
• Holding. If traffic or weather slows arrivals, planes may hold near the destination. See why is my plane circling?
• Late inbound aircraft. If your plane arrives late, the turnaround still takes time before it can leave.

Watch the estimate change

Add your flight to FlyingOver before you travel. While you're online you'll see updated estimates as the delay develops. In the air, without Wi-Fi, the app estimates progress from the saved route and schedule, and corrects it with live data once you're connected again.