The per diem that flight crews are reimbursed from their employer is given to them to cover or offset meals and incidental expenses (M&IE).  That per diem can be in one of two forms:

1. Taxable Per Diem
2. Non-Taxable Per Diem

Taxable per diem reimburses crewmembers for M&IE expenses that did NOT involve overnight travel away from their tax home.  When pilots or flight attendants fly day-trips, the per diem they receive is taxable per diem, and is included in Box 1 of the W-2 form (wages, tips, other compensation).

Taxable per diem does not influence the per diem deduction.  M&IE expenses are also not affected by trips that do not involve travel away from a pilot or flight attendant's tax home.  EZPerDiem.com automatically addresses this because day trips cannot be entered into the Per Diem Calculator.  In other words, day trips do not add to a flight crewmember's M&IE expenses or their per diem reimbursement.  As far as the per diem deduction is concerned, day-trips simply do not exist, and taxable per diem is simply part of a taxpayer's gross income.