United Airlines put its 787 back in the air on Monday, with both the airline and Boeing hoping to put the plane's four-month grounding behind them.

The flight from Houston to Chicago was just the kind of 787 flight that airlines are hoping for: uneventful.

Smoldering batteries on two 787s owned by other airlines prompted authorities to ground the planes in January. The failure of Boeing's newest, flashiest and most important plane embarrassed the company and its customers.

Both United CEO Jeff Smisek and Boeing CEO Jim McNerney were on board Monday's flight, and United promoted the plane's return to service.

Said Smisek, "I'll tell you, Jim, it was a fairly expensive piece of sculpture to have on the ground so we're really delighted to have it up and flying."

United is the only U.S. airline currently flying the 787.

The airline, based in Chicago, said it will use 787s on shorter domestic flights before resuming international flying June 10 with new Denver-to-Tokyo service as well as temporary Houston-to-London flights. It's adding flights to Tokyo, Shanghai, and Lagos, Nigeria, in August.

Those long international flights are the main reason the 787 exists. Its medium size and fuel efficiency are a good fit for long routes. Starting with shorter domestic flights "will give us a period to ramp up full 787 operations," United spokeswoman Christen David said.

Four of its six 787s have been fixed, and United said the other two will get the battery modification in coming days.

Airlines including Japan Airlines and South America's LATAM Airlines Group, said profit took a hit because of the grounding. LATAM said it still had to make payments on the plane and pay for crews and maintenance. It expects to resume flying soon.

United was forced to delay planned international flights, and the grounding reduced first-quarter earnings by $11 million.

The two battery incidents in January included an emergency landing of one plane, and a fire on another. Federal authorities lifted the grounding order on April 19 but it has taken Boeing and the airlines a few more weeks to fix most of them.

The incidents never caused any serious injuries. But the January grounding embarrassed Boeing and disrupted schedules at the eight airlines that were flying the planes. The company had delivered 50 of the planes worldwide.

The 787 uses more electricity than any other jet. And it makes more use of lithium-ion batteries than other jets to provide power for things like flight controls and a backup generator when its engines are shut down. Each 787 has two of the batteries.

Boeing Co. never did figure out the root cause of the battery incidents. Instead, it redesigned the battery and its charger. The idea was to eliminate all of the possible causes, 787 chief engineer Mike Sinnett said in an online chat on Thursday where he and a Boeing test pilot took questions about the plane.

The changes include more heat insulation between each cell and charging the battery to a lower maximum voltage.

Ethiopian Airlines resumed flying 787s on April 27, and Air India and Qatar Airways have also restarted flights. All Nippon Airways and Japan Airlines have both said they expect to restart 787 flights on June 1.

Boeing said that as of Sunday, 45 planes have gotten the battery fix out of 50 that were in service when they were grounded. It said it will finish the modifications by the end of May.

Boeing never stopped making 787s, but deliveries were halted. They resumed last week, and Boeing has since delivered two planes, both with the new battery system.

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Associated Press reporter Ramit Masti in Houston contributed to this report.