Nigeria's government has fined British Airways and Virgin Atlantic $135 million and $100 million, respectively, for allegedly overcharging passengers for flights between the African country and the UK.
Both airlines have strongly defended themselves against the allegation.
"We reject the allegations made by the Nigerian Civil Aviation Authority and we are vigorously defending our position," said BA in a statement.
"We remain committed to Nigeria and have been flying there for more than 75 years. We pride ourselves on offering competitive fares, a choice of products and connections to our Nigerian customers."
Added Virgin Atlantic: "We can confirm that we have received correspondence from the Nigerian Civil Aviation Authority relating to an enquiry surrounding historic passenger fuel surcharges.
"We have fully assisted the NCAA with its enquiry and we do not believe we have breached Nigerian law. We will be robustly defending any suggestion to the contrary."
Reports in the Nigerian press have pointed to an alleged dispute relating to the number of flights BA operates between Lagos and Heathrow and the number of slots on the route held by Nigeria's Arik Air.
Some reports claimed that BA had been forced to cut the number of frequencies on the route. However, a BA spokesman said: "We continue to fly to and from Lagos as normal."
The Nigerian CAA could not immediately be reached for comment.