Also look for provisions like this
WHERE THIS FARE IS COMBINED WITH ANOTHER FARE
THE PENALTY CONDITIONS /EXCEPT PENALTY FEE/ OF
EACH FARE COMPONENT APPLIES.
WHEN ONLY ONE FARE COMPONENT IS CHANGED THE
PENALTY FEE OF THE CHANGED FARE COMPONENT APPLIES.
WHEN MORE THAN ONE FARE COMPONENT IS BEING CHANGED
THE HIGHEST PENALTY FEE OF ALL CHANGED FARE
COMPONENTS WITHIN THE JOURNEY APPLIES.
So if there are multiple fare components and JL doesn't charge for penalty but AA does, you will be charged for AA's penalty.