Hundreds of off-duty Delta pilots picketed the airline at hubs across the country with more than 400 demonstrating in shifts outside the carrier's home base in Atlanta.
Delta pilots are on track to fly more overtime this year than they did in their two previous busiest years, due to the rebound in air travel.
As soon as this fall, the overtime hours will surpass those of the previous two years.
The airline has had to cancel thousands of flights since Memorial Day.
Delta pilots are concerned that their customers' plans have already been disrupted during the Independence Day holiday weekend. There is a perfect storm happening.
The union says that the disruptions are taking a toll on pilots' quality of life.
The union is currently trying to negotiate new terms with Delta to amend the current contract that was last negotiated back in 2016
Air travel has only gotten more busy since the last pay raise for Delta pilots.
Delta told Insider that the pilots' informational exercise would not affect its schedule and that it was aimed at keeping a strong balance sheet.
Many pilots carried signs saying they were ready to stop work if progress wasn't made. The ability of US airline pilots to strike is tied to a century-old railroad law.