What is E-TOP?

'ETOPS' stands for 'Extended Twin Engine Operations'. It's granted by the ICAO and FAA to those certified twin engine aircraft that are proved to be reliable and capable to fly continuously with only one engine running for a certain amount of time.

In early decades of aviation the sky was dominated by piston engine aircraft. And since 1930s trans Altantic flights had become popular. But the reliability of early piston engines was in doubt and in 1953 the FAA introduced the '60 minutes rule' to twin engined aircraft that their operation is limited to 60 minutes from any aerodrome. That means those flights needed alternative airports within 60 minutes of flight time along the way in case one of the engine failed. Into the era of jet, the performance of jet engine has been proving its reliability and in 1970s ICAO granted an '90 minute rule' in flavour of Airbus A300. In 1985 FAA first introduced the ETOPS with higher demand in terms of maintenance and aircraft performance. The first ETOPS boosted the 60 minutes restriction to 120 minutes, allowing twin engine jetliners to fly trans-Altantic routes which were exclusive to three/four engined aircraft. In 1988 FAA further eased off the restriction to 180 minutes, which virtually made 95% of the world surface are within the ETOPS-180 coverage.

In fact most of the modern twin engined jetliners are certified to fly under ETOPS rule. But airlines with higher maintenance standard and better safety record would be granted with higher ETOPS allowance. For example United Airlines' B777 are certified with ETOPS-207, which got 15% more than a normal B777, with 180 minutes.

Bear in mind that private and military jets are excluded from this regulation, though most of the European Union countries apply a ETOPS-120 restriction to private jets.

ETOP = extended twin-engine operations