Nationality?
Nationality has a role to play in all this. All the carriers you mentioned are going through a bit of financial difficulty as result there is a strong preference for Nigerian pilots. It doesn't make any financial sense to employ expats unless there is an urgent need for ready made pilots. Most Nigerian airlines have been expat heavy due to inability of their flight ops depts to come up with proper recruitment or training policies.
At the moment the Nigerian government is scrutinising the expatriate quota. Also the NCAA will not issue validations to low experience expats.
If you are nigerian then I believe the opportunities abound