This is from the v1.2 changelog, so i would assume from this that the times are pretty accurate
New feature, major upgrade to aircraft perfomance systems:
•The system on how aircraft performance data (speeds & fuel usage) are stored is rewritten. The new system is easier to administer and less subjective to bugs resulting from updates/changes to aircraft model data.
•Fuel consumption data for all aircraft models has been also recalculated as the storage format is different. This is partly still under checking as there is so much data but when the v.1.2 games start please keep an eye on the reported fuel usage values and report any discrepancies.
•This update is more technical than actual new feature as there is not much new & visible to users on this .. but still an important one.
•Bugs related to different aircraft cruise speed vs. actual flight time are fixed with this update. Whole fleet group of aircraft uses now the same speeds as the scheduled times must also match (so if for example B743 would cruise at mach 0.84 and B742 would cruise at mach 0.83 that unfortunately cannot be modeled - it's a tradeoff between ease of scheduling and 3-4 min difference in flight time).
•As previously posted here the a/c cruise speeds are now displayed in kts TAS and Mach (where applicable). This is for all models and makes comparison easier.
•Aircraft fuel consumption values are displayed to users with a note/info on how the data is actually calculated. It is (and has never been) just "fuel usage * flight time" but rather than 3-step calculation that involves climb, cruise and descent segments (even determines the wind component, taxi times, possible step climb, extra miles for flight routings and calculates the cruising level too!). This same 3-way calculation is present in v.1.2 performance module also but it is now more accurate - I would even say that it can be even used for flight planning purposes as the results are so close to reality on the couple of flights I have compared AWS vs. real life (this of course goes only with planes that have fully accurate data like A320 and other modern planes - older models have some data derived from other models / other sources).
•The displayed 'Average fuel burn' value is uniquely calculated for each aircraft model & variant. The value is calculated based on an 'actual' flight that is 200 nm long for very small planes, 450 nm for medium planes, 1000 nm for large planes and 3500 nm for very large planes. The system has precalculated this flight's true fuel consumption and flight time, and then converted this into an hourly fuel value for display purposes. This example flight and the displayed fuel value represents a general average of the fuel usage of the aircraft on it's normal flight routes.
•For actual route calculations on routes that players create the actual fuel used is always calculated according to the 3-way method described above - the "average fuel burn" value on aircraft pages is just an average / display value to give you some sort of rough estimate on the fuel burn. The true fuel burn depends always on each flight sector. (the actual fuel burn is not displayed to players but the actual fuel COST is however already stored and viewable in v.1.11 games with each route, day-by-day)