A jet at the bottom of the ocean is hardly what one should be calling a "mishap".
Mishap is the correct term to use in an aircraft accident no matter what the severity of the crash or damage. Althought it generally refers to an accident in which the damage exceeds $25,000, there are personal injuries which require hospitilization over 48 hours or there are broken bones other than nose, toes or fingers.
"mishap" is standard navy lingo for an accident.