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.

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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.

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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.

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