It comes after contract talks ended Thursday without an agreement.
American Airlines is the largest carrier at Philadelphia International Airport.
The two sides have been trying to come to an agreement for nearly a year.
Now, the union says its 28,000 members are one step closer to going on strike.
"After years of bargaining, including almost a year of mediated talks with the assistance of the National Mediation Board, and despite the Union's best efforts, American Airlines did not come to the table with an agreement that adequately compensates American's 28,000 Flight Attendants," said APFA National President Julie Hedrick.
American Airlines said it looks forward to continued negotiations.
The airline released a statement Thursday saying, "We made good progress in negotiations this week, adding even more to the industry leading proposal we've had on the table for months. We look forward to continuing negotiations so our flight attendants can benefit from the contract they deserve. This agreement is within reach and we look forward to additional dates being scheduled."