Complex sentence: Lockheed proposed a development of the Electra which was later placed into production as the P-3 Orion, which saw much greater success as it approaches nearly 50 years of front-line service.
Split into simpler sentences: Lockheed proposed a development of the Electra which was later placed into production as the P-3 Orion, which saw much greater success. The Orion approaches nearly 50 years of front-line service.