Long time lurker on this forum. Finally signed up.
I witnessed the final ~10 seconds of the flight before it crashed. Hope my description helps narrow down the scenarios of what may have happened.
Was driving northwards on Ring Road just west of the fuel depot at Sinamangal when I saw the plane fly very low across the airport buildings, turning from a northwesterly heading to a southwesterly heading. From my viewpoint It flew BEHIND the airport control tower, somewhere around the domestic terminal. (A taxi driver on the domestic parking lot reported that its wing almost touched the roof of the Nepal Airlines Hangar).
I lost sight of it briefly because of a tree, and then saw it flew towards me and across towards my right going very close to the southern corner of the international terminal, heading towards the runway near taxiway D, at a heading of perhaps 150 degrees. By that time the wings were level and the plane was slightly descending, but it appeared to be flying faster than a plane that was trying to land. Its sound was probably picked up on ATC audio while flying southwards on the west side of the tower (over the parking lot) I lost sight again as it disappeared behind higher terrain (The road I was on is lower than the runway), and seconds later saw a big plume of smoke from behind the runway.
Am trying to upload a sketch of what I saw but as a new poster here I don't seem to be able to post a link yet.
When the plane was doing the sharp turn left over the airport buildings my first thought was of the Transasia crash in Taipei.
Today I heard of witnesses talking about the plane buzzing Kapan hill (~4 km north of the runway 20 threshold) a few minutes before the crash, so it sounds like it may have flown north past the airport, did a turn towards 20 near Kapan hill, came back, missed 20, flew on towards the southern end of the airport or beyond, turned north again and appeared over the airport when I saw it (although I cannot tell whether it was aligned with the runway or not when it started its banked turn to the left over the airport buildings). Did it stall while doing the right turn over the airport buildings and was it too low to recover and then just aimed for an empty spot on the runway? At the time of the crash Jet Airways 266 had just pulled into position 1 (passengers disembarking), Thai was in position 2 (getting ready for take off), Malindo was backing out into the taxiway, while near taxiway E I saw one Buddha Air ATR and one smaller turboprop (most likely a Yeti J41) waiting to enter the runway.