Courtesy of Wikipedia:
A Flight Interruption Manifest (FIM) is a document issued by
an airline as a substitute ticket for passengers experiencing irregularities
during travel when the original ticket is not available. A FIM is generally
issued at a gate, ticket counter, or transit desk by an airline agent and will
note their original routing and ticket numbers, as well as those of the new
routing, thereby making the FIM the new ticket.
A FIM is only valid for a specific flight on a new airline
that is not the airline the ticket was originally issued with. For example, a
Delta gate agent could produce a FIM for a flight on United and send the data to
United. The FIM would then be accepted as a regular ticket on the specified
United flight.
Flight interruption manifests are perceived by both flying
passengers and airlines as becoming increasingly impractical, especially with
the widespread use of electronic ticketing, or e-Tickets. Producing a FIM
requires that the e-ticket be converted to a regular paper ticket and that the
data manually be sent to the receiving airline. Several carriers have announced
that they will be working together to smooth and digitize these
transactions.
And, again-- this time in English! A FIM is the ticket you get when your ticketing airline royally F's up, leaving you stranded. Some people call FIMing "Rule 240," however that term is pretty old school and isn't going to be understood by the fresh-out-of-college 22-year-old kid working the ticket counter.
Next time you find yourself stuck at O'hare on a four hour mechanical delay, tell 'em you that want to be FIM'd onto the next available flight (on ANY airline!) and away you'll go.
(If you want to get technical, here's what a FIM is: your ticketing airline reissues your original ticket for a ticket on a new airline because of a delay or cancellation on their part. They process the reissue [and pay the other airline to transport you] and then you go to the new airline and check in just like any other paying passenger. The remainder of your ticket remains the same-- the only part of your ticket that is modified are the segments in question.)
