DALLAS (CBSDFW.COM/AP) — American Airlines is cutting a key revenue estimate partly because of canceled flights due to the grounding of its Boeing 737 Max jets.

Fort Worth-based American said Tuesday that it canceled 1,200 flights during the quarter that ended March 31 because regulators grounded the Max planes.

It was just two days ago when the airline extended flight cancellations by removing the plane from its schedule through June 5 — six weeks longer than previous predicted — underlining that airlines think the Max will be parked longer than previously expected after deadly crashes in Indonesia and Ethiopia.

American has 24 of the Max jets in its fleet.

The airline says revenue for each seat flown one mile will be flat to up 1 percent, down from its initial forecast of flat to up 2 percent.

It also blames the government shutdown and 940 cancellations due to work on other Boeing planes.

(© Copyright 2019 CBS Broadcasting Inc. All Rights Reserved. The Associated Press contributed to this report.)