Never let the engine run more than once a month or two?

The engines were not running at the time of the fire.

The right engine ran for a further two more minutes, and then stopped as well.

He had no idea why the engines were still running.

Nobody would ever be out there while the engine was running, of course.

These must be the two that were on the ground with their engines running an hour ago.

The first complete engine finally ran on 26 March 1948.

The engine was still quietly running and nothing happened for a while.

Its engines were running when I arrived at about four.

The engine was still running, and I heard the doors being opened.