What is the problem?

Taxiing down the tarmac, the jetliner abruptly stopped,
turned around and returned to the gate. After an hour
long wait, it finally took off.

A concerned passenger asked the flight attendant,
"What was the problem?"

"The pilot was bothered by a noise he heard in the
engine," he explained. "It took us awhile to find
a new pilot."

P/S: this joke was from my aunt