Jessica Simpson Defends Kids In Coach During Awkward Flight With Ex Nick Lachey

Jessica Simpson is finally explaining why her kids were riding economy while she was chilling up front in first class during that awkward flight with ex Nick Lachey ... and according to her, blame Grandma!

We caught up with Jessica at the airport and she was cracking up over the whole thing -- insisting the seating setup wasn’t her doing because her mom booked the Hawaii trip as a treat for the family.

Clearly, Mama Simpson's first-class money only stretched so far ... but hey, a trip was still a nice gesture at the end of the day!

TBH, economy may have been the safer option for the kids considering Jessica unexpectedly shared the first class cabin with ex Nick -- we even told you, it was so awks that Jess swapped seats to avoid sitting near him.