This paper argues it's a poisson distribution:

Time-evolving distribution of time lags between commercial airline disasters[1]

while others disagree:

In the case of plane accidents, the authors of Ref. 7[1] found that the time lag between commercial airline disasters and their occurrence frequency could be well described by time-dependent Poisson events. On the other hand, authors of Ref. 8[3] have found that beyond certain timescales the time dynamics of both plane and car accidents are not Poissonian but instead long-range correlated.[2]

[1]http://arxiv.org/abs/physics/0509092

[2]http://arxiv.org/abs/0901.3183

[3]http://www.sciencedirect.com/science/article/pii/S0378437107...