President Donald Trump’s plan to accept a luxury aircraft from Qatar for use as a temporary Air Force One has opened a new front in the long-running battle over ethics and foreign influence in his presidency. The prospective gift—a Boeing 747-8 valued at roughly $400 million and dubbed “a palace in the sky”—would be among the most extravagant ever offered to a U.S. president by a foreign government. Trump has said the plane would be used solely by the Department of Defense during the transition to a new fleet of presidential aircraft and would later be donated to his presidential library. But critics across the political spectrum, including some Republicans, say the arrangement raises serious legal and constitutional questions—especially given Trump’s private business ties in the region and the shadow of past emoluments controversies.