Below is directly from Jet Blue's website. I have attached a link at the end that will take you right to the info on their site.



*** Blue Basic fares do not allow a carry-on bag if they were booked on or after 2/25/21 for travel 7/20/21 or later. Any carry-on bag brought to the gate (aside from a personal item that fits under the seat in front of you) will incur a fee and need to be checked. The fee is $65 (if it would be your 1st or 2nd checked bag) or $180 (if it’s your 3rd).

The only exceptions are:

Mosaic members (who get a carry-on bag and early boarding with all fares)
Travelers to/from London (including connecting flights)
Travelers that are combining a Blue Basic fare with an Even More® Space seat (on all legs, if connecting)
Active U.S. military
Unaccompanied minors
Please note, of the above exceptions, only Blue Basic customers who purchase an Even More® Space seat (on all legs, if connecting) are guaranteed to get their carry-on bag on board.


Jet Blue baggage info link