Complex sentence: This allows them to take off from the short runway of City Airport, which is located in the London Docklands area, stop for fuel in Shannon while passengers go through pre-clearance, and arrive in New York without the need to go through immigration or customs.
Split into simpler sentences: This allows them to take off from the short runway of City Airport, which is located in the London Docklands area and stop for fuel in Shannon. On the earlier flight passengers can use the stop to go through pre-clearance, and arrive in New York without the need to go through immigration or customs.