Halfway there.

The crew of the North American Eagle, a driving machine converted from a 1960s-era fighter jet, is aiming to break the all-time land-speed record of 763 mph.

Their racer recently clocked 400 mph during tests in Southern California.

“That was a pretty big deal,” said Cameron Shadle of Everett, a Boeing worker who is on the North American Eagle’s crew. “With all this testing, we’re trying to work up to the higher speeds and do it safely without hurting anybody. The faster we can get the car going and not have any problems, that’s a huge milestone.”

Last week, the North American Eagle — a former F-104 Starfighter that is kept at a small airport in Spanaway — was at the El Mirage Dry Lake in California’s Mojave Desert for three days of tests.

Although plenty of complications arose, the test results will help the crew attain its goal of setting the land-speed record — an attempt that, at this point, will likely happen next year.

“The progress of the technology only has a certain speed,” said driver Ed Shadle of Spanaway, Cameron Shadle’s father. “We can only go as fast as technology allows us to go.”

The first two days of testing, Tuesday and Wednesday, didn’t go as planned.

On Tuesday, the land-speed racer nearly lost control. The surface of the lake bed was rough and uneven after being chewed up by other off-road vehicles.

“It was so wild, my feet flew off of the rudder pedals,” Ed Shadle said. “I was bouncing around in the cockpit like a madman. I was to the point of thinking, ‘If I don’t get this thing under control, I’m going to crash.’ “

The next day was better. Crew members plotted a new five-mile course that was in better condition than the previous route, but high temperatures caused several of the racer’s electrical systems to fail. Still, Shadle was able to briefly ignite his afterburner and reach 250 mph.

Then came Thursday’s tests.

Temperatures cooled to 96 degrees, and the course was nice and smooth. Shadle fired up the afterburner for a full 5 seconds, shooting the North American Eagle across the dry lake bed at speeds up to 400 mph — its fastest speed yet.

“It went straight as an arrow and fast as a rocket ship,” Ed Shadle said. “It was a very good run.”

The only downside to the final test run was that the high-speed parachute failed to deploy. Fortunately, the North American Eagle’s magnetic braking system provided enough resistance to bring the vehicle to a halt.

“We finally got some good computer data that is usable data to tell us what the car is doing,” Cameron Shadle said.

A few dignitaries came out to El Mirage to watch the tests.

Retired test pilot Bob Gilliland, the first person to fly the SR-71 Blackbird — a giant black spy plane that looks like something straight out of a Batman film — came to watch some runs.

The daughter of famous test pilot Scott Crossfield, who flew the North American Eagle when it used to be a fighter jet, also stopped by, Ed Shadle said.

This fall, the crew plans on heading out to the Black Rock Desert in Nevada for more high-speed tests. Eventually, the crew also plans to travel to Canada to pick up a new jet engine for the racer.

Crew members are more confident than ever in their ability to break the land-speed record.

“It’s got enough horsepower. That’s not a problem at all,” Ed Shadle said. “It will do its job.”