You cut buy yourself a parachute, and take it with you onboard. Most airlines allow this.
In the case of a foreseeable mid-air breakup, you then would have a chance to survive.
Fully pressurized crashes won't give you a chance for escape, however, as you won't
be able to open the emergency doors.
On the other hand, you could try to smuggle an elephant-grade shotgun onboard, to open
an escape hatch for yourself Willis-style. While I would not recommend that, I ask you to
film the check-in inspection and post your results on the forum, in case you choose to go
for the latter.