Complex sentence: The initial specification called for an airship with a disposable lift of 5 tons (5080 kg) capable of flying at and maintaining an altitude of for 30 minutes; however, the required load was later reduced to 3.1 tons (3150 kg).
Split into simpler sentences: The initial specification called for an airship with a disposable lift of 5 tons (5080 kg) capable of flying at and maintaining an altitude of for thirty minutes. The required load was later reduced to 3.1 tons (3150 kg).