On 5th June, 2015, Aero Contractors Company of Nigeria Ltd. scheduled commercial flight NIG181, a Boeing 737-500 aircraft with registration number 5N-BLE from Lagos to Kaduna, took off at 1828hrs with 108 passengers and 5 crew on board. The First Officer was the pilot flying. The flight operated on an Instrument Flight Rules (IFR).
ATC cleared NIG181 as follows: to climb and maintain FL350 after departure, to make a right turn on a heading of 330o, thereafter instructed to make a further right turn on a heading of 360o and cleared on course via IBA1.
During the initial climb, the Captain observed that the cabin rate of climb was zero but later indicated normal. However, the First Officer reported that on reaching FL150, he observed that the cabin altitude was indicating about 3000ft and since this occurred at low altitude, they decided to monitor during climb.