Menendez spokeswoman Tricia Enright told the AP that the senator paid for the two trips on the donor’s plane out of his personal account.

NBC News reported that Menendez wrote a check to Dr. Salomon Melgen this month after aides reviewed his flight schedule in response to a complaint filed with the Senate Ethics Committee last November.

Dan O’Brien, Menendez’s chief of staff, told NBC News that he was “chalking it up to an oversight.” 

Earlier Wednesday, Menendez defended his relationship with Melgen, who is under investigation by the FBI.

In a statement, Menendez’s office described Dr. Salomon Melgen as “a friend and political supporter” of the senator’s for many years.

Melgen is suspected of providing free trips and even underage Dominican Republic prostitutes to Menendez, according to a complaint lodged with the Justice Department by a Washington D.C. watchdog group last year.

Menendez denied those allegations, saying they were manufactured by the conservative media website The Daily Caller ahead of his election last November.