That "gunk" affected the track on the ground "that locks the seats to the aircraft floor," she said.
"We are taking extra steps to ensure that the seats do not dislodge from the track."
Seats on at least three American Airlines flights have become loose recently, unnerving passengers in the latest of a string of woes for American. The airline has also been beset in recent months by labor troubles, delays and flight cancellations.
- CNN's Carma Hassan contributed to this report.