Fresh revelations indicated on Tuesday that Petroleum Minister, Mrs. Diezani Alison-Madueke, maintained a second jet.
The jet, a Global Express XRS plane, is allegedly chartered specifically for her private and official trips overseas.
A return trip on the XRS plane is said to cost taxpayers €600,000.
The jet is different from the Challenger 850, which the House of Representatives said gulped N10bn in the last two years to fly the minister.
Investigation showed that the House Committee on Public Accounts stumbled on the second jet in the course of the ongoing probe into the N10bn expenditure on Challenger 850.
Findings also showed that the owners of Challenger 850 might have fled the country shortly after the House ordered an investigation into the transaction between them and Alison-Madueke.
It was gathered that the aircraft owners reportedly became jittery after the committee declared its plan to summon them to assist in the investigation.
However, a document our correspondent obtained in Abuja on Tuesday, indicated that Alison-Madueke flew in Global Express XRS on two occasions in 2011.
She chartered the same jet twice in 2013 on a return trip bill of €600,000 per trip.
Abuja lawmakers shocked and are curious about how a serving minister raised the money to charter jets for overseas trips at the expense of the taxpayers.
It was further learnt that those who accompanied Alison-Madueke on the trips would also be invited by the committee to assist with the investigation.
Alison-Madueke is accused of spending about €500,000 monthly to maintain the first aircraft.
The Nigerian National Petroleum Corporation had on Monday denied the allegation but said it had the legal right to own or charter an aircraft for its operations.
“This practice is common and acceptable in the local and international business environment in which it operates. There is nothing prohibiting the NNPC from owning or chartering an aircraft,” the NNPC had said in a statement by its Acting Group General Manager, Public Affairs Division, Omar Ibrahim.