A man who piloted a wealthy eye doctor’s private plane testified on Wednesday that Sen. Bob Menendez was a frequent passenger who flew for free. Prosecutors say these free plane rides were how a wealthy benefactor, Dr. Salomon Melgen, who is also on trial, bribed the Democratic senator for favors.

The pilot, Robert Nylund, said Melgen made sure the plane was stocked with Menendez’s favorite brand of water, Evian, to make sure he was comfortable while aboard, CNN reports. Nylund also told the court he once flew Menendez from West Palm Beach to Washington DC, a trip that cost Melgen $8,6036.02. The senator was the only passenger on that 2010 flight. This trip required the plane to be flown with no passengers on the flight to West Palm Beach in order to pick up Menendez. After dropping off the Democratic senator, the plane was flown empty to its hanger in New York.

The wealthy eye doctor flew Menendez on his private plane frequently. Nylund said he flew the senator 16 times while he worked for the ophthalmologist.

Prosecutors say Melgen, who was convicted of Medicare fraud earlier this year, bribed Menendez with private plane rides, a vacation in Paris, and luxury trips to the Dominican Republic. In exchange, Menendez allegedly lobbied the U.S. State Department to get the married, wealthy eye doctor’s girlfriends U.S. visas. He also allegedly intervened in a $8.9 million billing dispute in 2011, a year after the pricey private flight paid for by Melgen took place.

New Jersey Gov. Chris Christie could chose a Republican to replace Menendez, if his seat becomes vacant, a move that shift the politics of the U.S. Senate.