Last month I booked a flight on American Airlines for the end of December. Today I got an email from them stating that there had been a change in my trip, and here are the updated details of my flights.
For both flights (IAD->LAX and LAX->SYD), the only change I can see is that the departure and arrival times have changed slightly (<30 minutes). The aircraft did not change either, but both flights are now longer! The first flight gained 49 minutes and the second flight gained 10 minutes.
10 minutes on a 15 hour flight is negligible, but adding almost an hour to what was a 5.5 hour flight seems like quite a lot! Why would an airline change their flight time so drastically, when seemingly nothing but the departure time has changed?