American Airlines has cooperated with Google Research and Breakthrough Energy to test whether atmospheric zones likely to create contrails can be avoided.
United recently reached a deal with its pilots that provides cumulative 34.5%-40.2% increases in pay rates over four years that American's pilots seek to match.
American Airlines, Delta Air Lines and United Airlines collectively spent $2.1 billion on maintenance in the second quarter, according to investment bank Jefferies.
JetBlue Airways and American Airlines are proceeding with a wind-down of their Northeast Alliance (NEA), though the two remain split on a decision to appeal.