A Russian Su-24 all-weather attack jet crashed Monday killing both pilots and bumping up the tally of Russian military that have crashed in the past month to five.

The Su-24 crashed shortly after taking off in western Russia near Khabarovsk. Another Russian Su-24 crashed in February.

Monday’s crash was one of five to have occurred in a Russian air force fleet that is showing its age since military leaders have increased exercises and flights.

Two MiG-29s fighter jets, a Tu-95 Bear bomber and a Su-34 Fullback heavy strike fighter have crashed over the past month. The Russians temporarily grounded their MiG-29 and Tu-95 fleets to investigate the causes of the crashes.