Every time I fly (Delta), the captain comes on and as well as the general welcome stuff, weather at destination etc., he says something like "and the flight time will be xx hours and yy minutes".

I've often wondered how accurate that is, for surely "10 hours and 58 minutes" can't be right, so why not say "around 11 hours".??

Anyway, I just came back from NRT to LAX, and the captain announced "flight time 9 hours 12 minutes". So, I set that time in my timer app, and on wheels up hit Start.

I stopped it when we touched down.

9 hours, 12 minutes, 20 seconds later.

I was impressed.

It's accurate as of the time it's given. The flight time is provided based on sophisticated software and a flight plan. Needless to say, if there are changes to the flight plan, the times change accordingly.

That number the captain says comes straight off the flight plan or Flight Management Computer and takes into account flight plans and winds en route. If the flight is flown exactly as the computer expects it can be scary how accurate everything is.

Ive seen flight time exactly match and fuel figures within 0.5% of estimated. But if flying into a congested airspace, ATC separation requirements and not ideal vectoring can throw that off a little bit.

This.

When I used to do transcons every week, for 2+ years, I got in a habit of clocking the time with my chronometer, just out of curiosity. Barring any obvious deviations, it was amazing how often it was dead-on accurate.

I regularly fly long haul and I find the variation flying to SFO is generally less than 10 minutes from wheels up to wheels down. However, flying to LHR it's a very different matter as it depends entirely on how long the ATC hold is when you arrive.

Does it account for ATC holds at the destination airport - like is it able to predict based off the time of arrival and how many other flights will be landing at the same time how long they'll have to hold until they can land? Now that would make it even more impressive than it already is.

As a software engineer, I'm not at all surprised that the flight times are incredibly accurate. It's just math (a more complicated version of the "train leaves the station" problem from algebra class)! They feed all the flight information into the computer, and (other than obvious reasons, such as any deviations in the flight plan) there's no reason for the flight time to be inaccurate.

The math can't predict ATC holds, however. Those decisions have nothing to do with the flight plan and are often made and/or revised in the last few minutes of flight.

I use my phone's timer when flying. The captain says our flight time is 2:38, I run a timer for 2:38. Sometimes it's off by a few minutes, but usually it's dead on. Last flight I was on was literally perfect, the wheels touched down as the timer hit 0:00.

I'm a software engineer too, but with so many variables, I'm surprised it's accurate down to a few minutes. Guess I underestimated the brilliance of my own kind.

No, it's based on the calculated flight plan - speed and distance. The captain will often say that this is the planned time, unless we need to hold for traffic, divert around weather, etc.

What an earlier poster said its true that the pilot gets the flying time or gate to gate time off the Flight Management System.

When the aircraft has Airshow I turn it on at the gate and while we're taxing to the runway it shows Distance to Desitnation, Estimated Time of Arrival and Time to Destination. All of this information is relayed from the Flight Management System. All Airshow is doing is translating the information from the Flight Management System into data that is easy to decipher for the passenger.

If the Flight Management System is setup for a destination using the Metric System Airshow knows from the airport data entered what to display.

Airshow also has other features that activate automatically such as when the pilot turns on and off the fasten seatbelt Airshow can automatically display the Fasten Seatbelt Message.

When the plane is on the intiial descent Airshow knows to display" We will soon be landing in San Francisco . Thank You For Flying United Airlines. Then getting the latest information from the Flight Management System it will display the connecting gate information.

As I recall in an Inflight Guide on an airline under the Inflight Entertainment Map Feature it said that Arrival Information is updated at the pilot's request and to check the monitors in the terminal for the latest updated information.

I think there is also some way to program Airshow to display the Take Off Runway, Estimated Taxi time to Active Runway or Gate. Possibly there is a way to add the Estimated wait time at Customs for Citizens and Foreigners as well as Estimated Connection Time etc and any weather delays etc.

So yes the Flight Management system is the heart of the information.

Flight time is given right on the dispatch release. FMS will have flight time as long as correct winds have been entered.