Aer Lingus is among a group of airlines which are participating in an investigation into alleged cartel activity in air cargo by the US Department of Justice.
The investigation was announced on February 14th and is ongoing.
Several major airlines and cargo specialists have been contacted by the US Department of Justice during the investigation so far.
Yesterday it was disclosed that a separate investigation has begun into fuel surcharges in the airline industry.
This investigation is being conducted again by the US Department of Justice, along with the UK Office of Fair Trading (OFT).
An Aer Lingus spokeswoman said: "Aer Lingus has recently received a subpoena from the US Department of Justice in connection with an investigation into the air cargo industry. "Aer Lingus is fully co-operating with this investigation. We have not receive any communication from any authority in relation to an investigation into alleged price fixing on passenger fares."
This second investigation concerning fuel surcharges involves British Airways, Virgin Atlantic and United Airlines.
The OFT said in a statement yesterday: "The OFT can confirm that it is conducting both a criminal and civil investigation into alleged price coordination by airlines in relation to fuel surcharges for long-haul passenger flights to and from the UK."
It said its civil investigation was being conducted under the Competition Act 1998 and Article 81 of the EC Treaty.
The criminal investigation is being conducted under the Enterprise Act 2002.
"No assumption should be made that there has been an infringement of competition law," the regulator said.
"The OFT will not be in a position to conclude whether the law has in fact been infringed until it has completed its investigations and assessed the available evidence."
British Airways said its policy was to conduct its business in full compliance with all applicable competition laws and it was assisting the UK and US authorities with their investigations.
The airline said commercial director Martin George and head of communications Iain Burns had been given leave of absence during the investigation, but declined to say why this step was taken.
However, a spokeswoman for the OFT said: "We are conducting an investigation both on the criminal and civil side. Criminal investigations are by definition carried out against individuals."
