Plot hole: The Mummy would not know where to crash the plane in England to retrieve the dagger from the Abbey as this was placed there thousands of years after her imprisonment. If she did know it was there using her powers she would know that the stone was missing, but she didn't.
Suggested correction: Ahmanet did know where to crash the plane. She had the ability of sensing the dagger. Jenny even points out to Nick that Ahmanet knew where to find it. Ahmanet's powers are not fully explained but, since she could sense the dagger, she probably thought the stone was still with it but didn't know until she tried to stab Nick. Later, when the Prodigium agents find the stone, Ahmanet could not only sense it but, told Jenny it was found.
Plot hole: When the C-130 transport is falling from the sky, the Egyptian sarcophagus remains lashed to the plane's cargo deck. The crew exploring the wreckage says they are miles from the 'primary crash site' (so that nasty stuff can happen to them without witnesses). The sarcophagus would still be at the primary crash site, along with the remains of the fuselage and cargo deck. (00:32:50 - 00:36:00)
Suggested correction: We don't see where the sarcophagus went when the plane crashed, so it could have broken free from the plane earlier and landed along with other parts.
