Is there any scenario where a user would insert “NAV/D1E99A1” in Item 18 as an RNAV value?
Any operator capable of RNAV 1 can file E2 or E1 (we recommend “E2”), but it would not be an error to file E99 and the FPL would be accepted. Please note that we request you file your maximum RNAV capability in Item 18. Filing E99 would make the flight ineligible for any portions of an RNAV Standard Instrument Departure (SID) or Standard Terminal Arrival Route (STAR,) which extend into the en route environment. Please refer to guidance on this website at Filing Instructions/Reference Guide/RNAV Requirements.