WASHINGTON — The Dwight D. Eisenhower carrier strike group chopped out of the European theater of operations Dec. 26 and headed home to Norfolk after months of operating in the Arabian Gulf and the Mediterranean, where the strike jets of Carrier Air Wing 3 flew hundreds of missions against Islamic State group targets in Syria and Iraq. The homecoming is set for Dec. 30 — two days shy of the Navy's stated goal of bringing the group home in seven months.

US carrier groups regularly relieve each other in theater, often handing off duties within sight of the other in the Arabian Gulf or Arabian Sea. But this time, no carrier is in the Eisenhower's wake.

The relief ship, the carrier George H. W. Bush, has yet to leave Norfolk, and it's unlikely to do so before the Jan. 20 presidential inauguration of Donald Trump, according to a Navy source. The gap could last as long as two months, sources said, between the time the Eisenhower left the combat theater and the Bush arrives.

And that gap comes at a particularly inopportune time. Numerous media reports indicate intelligence organizations and analysts are on the lookout for provocative actions by potential antagonists — in particular Russia, China, North Korea, Iran or ISIS. Terror alerts, according to media reports, are high in many regions, including Europe, the Middle East and North America, due to a confluence of factors — the new year, ISIS' diminishing power in the face of counterattacks in Iraq and Syria, and a natural tendency to test a new administration.

Other Central Command carrier gaps have taken place in the past, usually when a strike group is needed elsewhere or maintenance issues at home have forced ships to deploy late. The Pentagon plans for such events, often dispatching expeditionary US Air Force units to the region to pick up the slack — something that seems to have taken place now.

The newest gap is not a surprise, and actually has been months in the making — arguably well over a year. The Bush entered Norfolk Naval Shipyard in Virginia in mid-June 2015 for what started out as a planned six-month repair period, extended just before it began to eight months. Facing a scheduled early-December 2016 departure date to relieve the Eisenhower group, the initial delay seemed manageable, giving the group nearly nine months to work through the predeployment training cycle.

But the overhaul dragged on well past the March completion date. Navy officials have been sparing at best and sometimes contradictory in explaining why the overhaul took so long — the explanations complicated by multiple oversight commands, including Naval Nuclear Reactors, Naval Sea Systems Command, Naval Air Forces and US Fleet Forces Command. The reasons given ranged from poor planning to emergent work — often unspecified — to the lack of enough trained personnel at Norfolk Naval Shipyard due to previous layoffs and funding interruptions.

In the event, the Bush finally left the shipyard July 23 after more than 13 months in overhaul, facing a drastically compressed training period if the early December date could be met. But the command responsible for training the Bush and her strike group, US Fleet Forces Command, apparently did not have a plan in hand to deal with the short training cycle, although something called the Optimized Fleet Response Plan is supposed to deal with such eventualities. According to several sources, Fleet Forces didn't hold a major meeting of all parties to determine a way ahead until late August.

Fleet Forces Command has declined numerous requests for comment on the Bush's situation. The command has not issued a direct statement on its plans for the Bush.

Among the obstacles in getting the training going, several sources said, were defects on the carrier that remained unaddressed during the overhaul.

The Bush is not alone in experiencing delays. The Eisenhower itself missed a deployment due to shipyard and maintenance issues, and had to be spelled in 2015 by the carrier Harry S. Truman. Chronic problems in the Navy's four shipyards, which perform the majority of heavy maintenance work on the carriers, has meant that most recent carrier overhauls are running long. Naval Sea Systems Command has acknowledged these problems and is working to restore and improve the workforces in the yards.

But it is not clear why Fleet Forces did not have a training plan in hand even before the Bush returned to the fleet. The ship and its strike group completed their last major predeployment exercise Dec. 21, but Navy officials expect another month to go by before the Bush deploys.

 The Navy did not respond to a request for comment before press time.