Mexico assess a Tourist Tax for flights into Mexico. Airline include this of fares purchased in the US.
There are a few exemptions, Mexican Citizens and residents, infants under 2, diplomats and transfer passengers under 24 hours.
Most airlines process the refund of this tax upon submitting proof (such as a Mexico Passport). Not and Issue with AA, UA or Delta.
Interjet initially refused. They said to go get it form the Mexican Government. It is their obligation to collect it and NOT to collect it as appropriate.
If you find yourself in this situation and they refuse, I suggest you file a DOT complaint and if necessary take them to small claims court. They are registered in the US as ABC AEROLINEAS, S.A. DE C.V.
It is a small amount of approximately $28 per passenger, and should be a simple issue, but they arrogantly ignored it. Likely betting that consumers will not pursue such an amount.
Took some effort but they finally refunded this tax on several tickets. Just FYI.