Like rj said, it's far more of a nuisance than anything else.
The only critical time, just like any other plane, is a failure on takeoff. Or if it's uncontained, like rj said.
However, in the 400 that rj flies, they just have the butler hand them a checklist, light their pipes, and continue on.
On the classic, we climb out on the wing with a set of tools and work on the motor in flight.
