The U.S. is shipping the largest amount of crude oil to Europe since Washington ended its ban on exports more than six years ago as buyers seek alternatives to Russian supplies.

In April, U.S. producers exported nearly 50 million barrels of crude to European buyers from major terminals in Texas and Louisiana, according to ship tracking data compiled by Bloomberg. That’s nearly half of what was sent overseas last month from the Gulf Coast, the main U.S. export hub.

Supply options for Europe have shriveled up as buyers on the continent shun oil from Russia following its invasion of Ukraine, worsening an already tight supply picture. Despite the region’s reliance on Russian energy supplies, some countries are calling for a stronger response to the war, including an official oil ban. Meanwhile, North Sea crude supplies are set to tumble in June to the lowest level in over a decade due to maintenance in several of the area’s oil fields.

With U.S. crude output forecast to increase, flow volumes to Europe should continue to grow, plugging gaps left by geopolitical issues and fundamentals.

The shipments to Europe last month included three Very Large Crude Carriers—the biggest ships serving the industry—for the first time in monthly data. Those supertankers, known as VLCCs, can each carry 2 million barrels.