The disappearance of an AirAsia jetliner while flying over the Java Sea on Sunday is probably due to stormy weather, but there were also some unusual factors, aviation experts speculated Monday.

Based on information known so far, the pilots of AirAsia Flight QZ8501, which was about an hour into the flight from Surabaya to Singapore, informed ground traffic controllers they wanted to take the plane up to 38,000 feet from 32,000 amid bad weather. Aviation analysts said pilots would usually try to fly around a thunderstorm or turbulence rather than through it.

It is also unusual there has been no sign of the plane or debris from the wreckage after more than 24 hours had passed as the Java Sea at the location has quite brisk sea traffic.