The first one was Spirit Airlines Flight 970. The aircraft involved, registered as N823NK, was an MD-82 flying in mid day in June 2002 when it suffered a loss of thrust on both engines, in cruise at an altitude of 33,000 ft, that is about 10,000 m. The two pressure sensors, located on the engine nose bullets, were blocked by ice crystals, leading to incorrect indications and over-estimation of the EPR. The crew noticed the drop in speed and the precursor indications of a stall just before disengagement of the autopilot and putting the aeroplane into a descent. They had not activated the engine anti-ice systems. The second one involved was an MD-83 operated by Swiftair that occurred in June 2014. The crew was aware of the drop of their airspeed and successfully recovered. French BEA revealed that there were several technical defects on the plane, several of which were on the EPR system. On 21 July 2013, BEA noted that there was intermittent failures on the autothrottle that led to the replacement of the EPR transmitter on No.2 engine. On 19 October 2013, the No.1 engine EPR indicator was faulty (no display of values) and the display was replaced. On 2 March 2014, the autothrottle actuator was replaced. During the recommissioning process, the "EPR LH" failure message was displayed. The left-hand EPR transmitter was therefore also replaced. Additionally, on 27 June 2014, an engine surge resulted in a rejected take off, at about 80 knots. Due to this, No.1 engine, was replaced. The following was the sequence of events based on the FDR analysis: The crew had been prepared to fly to Algiers from Ouagadougou. As the crew would fly to Algiers, they should know the weather condition in the area. The crew had arrived in Algiers one hour earlier, and knew about the weather in the region. Therefore, they had already known the risks of turbulence and icing while flying in the region. After handling the ground clearance, AH5017 finally took off from Ouagadougou at 01:15 local time (same time as UTC). There were no incidents in its initial climb.  13 minutes after take off, while climbing through FL215, AH5017 slightly deviated to the left to avoid a storm in the area. They reported this to Ouagadougou ACC. However, even though they knew that a storm had occurred in the area, the flight crews did not activate the engine anti-icing system.