​NEWARK, N.J. — ​Sen. Robert Menendez’s environmental record took a hit on Wednesday after it emerged at his federal corruption trial that he once took an ​eight-passenger private jet from West Palm Beach to Washington​,​ D​.​C​.​ — by his lonesome.

The 2010 Cessna flight, which cost $8,036.82, required three leg​​s, including ​one segment with no passengers ​just ​to get the jet to West Palm Beach, and a leg with no passengers to get the plane back to its h​​ang​ar in Islip, ​on Long Island.

The $2,600-an-hour flight was arranged by and paid for by the New Jersey senator’s wealthy pal and co-defendant ​​Dr. Salomon Melgen, records showed.

Menendez​ and Melgen, ​both ​63, are on trial in Newark federal court on charges that Melgen bribed the ​Garden State ​pol with lavish gifts, including private jet flights, all-expense-paid vacations and $750,000 in campaign contributions.

In exchange, Menendez, a Democrat​, used the power of his office to ​help ​Melgen with his business and personal affairs, including visas for three foreign​ girlfriends, prosecutors have alleged.