TDY is the acronym for a temporary duty
assignment used in the airline industry. It is not necessarily the same as
a temporary assignment
as defined by the IRS.
It is important for crewmembers to distinguish between the two. A TDY as
used in the airline industry has no hard rules about time while the IRS
definition of a temporary assignment does. If a crewmember on TDY wants to
write off travel
expenses associated with getting to their temporary base, they must ensure
that the TDY assignment also meets the time requirements of a temporary
assignment as defined in
IRS Publication
463.
To understand this, it is important to
understand the concept of a
tax home. Generally a pilot or flight attendant's tax home is their
domicile, but in the case
of a temporary assignment, that might or might not be true.