I'm sure many people know what can happen when you cross a sim boundary at speed. If you don't, then the word fragmentation, neatly explains it. Coals pictures and blog post will give you an idea.
Cubey Terra one of the Grids major aircraft makers, has grounded his fleet of self guided planes, and blimps from Qarl have been gone for quite a while.
Now that landowners have the ability to block almost anything coming on their parcels, air travel is somewhat more, lets say, adventurous.
I admit I got a little tired of my plane ( and sometimes my clothes ), disappearing in midflight, and have not flown it for some time.
The Lindens are aware of the problem, and will I hope find a solution.
EDIT:- To spread around some credit, Apotheus Silverman scripted some of the planes. The Terrachute as well, that saved me from the embarrassment of going splat a few times
Pilots will not wear spurs in the cockpit - 1920s RAF Cadet Flying manual