PORTLAND, Maine — More than a dozen vessels were deployed off the New England coast Wednesday in a drill to test their abilities to respond to a massive oil spill at sea.

The so-called Spill of National Significance Exercise in Portland Harbor was held 21 years to the day the Exxon Valdez ran aground off Alaska, leaking 11 million gallons of crude oil in the nation’s worst oil spill.

The Maine Responder, an oil spill-cleanup vessel, joined other boats in wet, blustery weather to counter a simulated collision between an oil tanker and a ship carrying cars resulting in nearly 3 million gallons of oil being leaked.

In reality, there was no oil tanker, no car carrier and no oil spilled. But the vessels and the “spill” were tracked with computers to measure the performance of more than 50 federal and state agencies and private organizations.

The exercise is held every three years and takes more than a year of planning. This is the first time it has been held in New England, a region that has a lot at stake with its rich natural resources and fishing and tourism industries.

More than 600 people participated in the exercise, and the results will be used by decision-makers in Washington on how best to respond to catastrophic oil spills.

“This is the Super Bowl of oil spill exercises,” said Coast Guard Capt. Jim McPherson, who oversaw operations in Portland. “It doesn’t get any bigger than this.”

The exercise is mandated as part of the Oil Prevention Act of 1990, which was passed following the Exxon Valdez disaster. Previous exercises have taken place in Pennsylvania, Alaska, Texas, California and on Lake Michigan.

Wednesday’s drill included the Maine Responder, a 208-foot ship armed with thousands of feet of booms to contain and absorb spills and with equipment to suck oil off the water.

The ship, berthed in Portland and tasked with responding to spills throughout the Northeast, was deployed in Portland Harbor with smaller oil boom and skimming vessels.

Other vessels were sent to strategic points in Maine south and north of Portland, while still more were deployed in Boston and Rye, N.H., to prepare for a spill spreading south to those waters.

At the same time, more than 200 people from federal and state agencies worked out of a command center that was set up in a large room at a Portland Holiday Inn, where officials monitored and directed the ships. Besides testing the capabilities of the vessels, the drill aims to test the coordination among the multiple federal and state agencies that would be involved in an actual spill.

The weather forced the cancellation of two planned flyovers by a reconnaissance aircraft that were part of the drill.