Complex sentence: A "scram" order was also issued to bomber units still airborne; it signified a warning to number crews that intruders were in the vicinity and they were to divert to airfields in western or southern England, and out of danger.
Split into simpler sentences: A "scram" order was also issued to bomber units still airborne. It signified a warning to number crews that intruders were in the vicinity and they were to divert to airfields in western or southern England, and out of danger.