Air jet system

The aircraft was involved in a mid-air collision with a Corporate Jet over Senegal. While the 737 landed safely, the latter aircraft later crashed in sea killing all seven on board.

The collision is due to the Hawker HS-125 (6V-AIM)’s non-compliance with its flight level. The Boeing 737-800 (3C-LLY) was assigned flight level 350. 
At 18H01’11¨, 6V-AIM had confirmed ATC to maintain the 340. The 3C-LLY CBD claimed to have seen it come down on them. Only flight recorders could have helped to determine how such a situation may have occurred; Unfortunately, they disappeared with the plane.
The lack of altimetry may have contributed to the collision in flight.

On January 2016, the Senegal Bureau d’enquête et d’Analyse (BEA) reported an update to the current investigation process. 

An air-start system is a power source used to provide the initial rotation to start large diesel and gas turbine engines.

Compared to a gasoline (petrol) engine, a Diesel engine has a very high compression ratio , an essential design feature, as it is the heat of compression that ignites the fuel. An electric starter with sufficient power to "crank" a large Diesel engine would itself be so large as to be impractical, thus the need for an alternative system.

When starting the engine, compressed air is admitted to whichever cylinder has a piston just over top dead center , forcing it downward. [1] As the engine starts to turn, the air-start valve on the next cylinder in line opens to continue the rotation. After several rotations, fuel is injected into the cylinders, the engine starts running and the air is cut off.

There are an estimated 15,000 business jets available for charter in the worldwide fleet. The US market is the largest and the European market is the second largest, with growing activity in the Middle East, Asia, and Central America. [3]