Tributes have been paid to three Britons killed in a helicopter crash in the Grand Canyon, as their three fellow travellers and the American pilot lay critically injured in hospital.

Becky Dobson, 27, her boyfriend, Stuart Hill, 30, and his brother, Jason Hill, 32, died when the tour helicopter they were riding in crashed near Quartermaster Canyon, by the Grand Canyon’s west rim, on the lands of the Hualapai nation, early on Saturday evening.

After a rescue operation hampered by strong winds and rough terrain, their friends Ellie Milward, 29, Jonathan Udall, 32, and Jennifer Barham, 39, and the pilot, Scott Booth, 42, were airlifted to University Medical Center in Las Vegas, Nevada, where they are said to be in a critical condition.

A picture taken just after the crash shows how one woman was apparently able to walk away from the wreckage as it was engulfed in flames.

David Hill described his two sons, who were born 22 months apart, as inseparable. “They and a group of friends had all flown out to celebrate Stuart’s birthday and it was part of the trip for them to all go on a helicopter tour of the Grand Canyon,” he said.

Play Video 0:45 Three people killed in Grand Canyon helicopter crash – video report

“Jason worked as a solicitor and Stuart worked as a car salesman. They both lived very successful lives. We were so proud of them. We are so lucky to have had our boys for 30 years. We are so heartbroken.”

Dobson’s father, Peter, said his daughter was “full of life and looking forward to going to Vegas for her boyfriend’s 30th birthday to celebrate”.

“They just went for a long weekend, a four-night break,” he said. “They were staying in Vegas, they had been looking forward to it for a long time.” The couple lived together in Worthing, West Sussex. “They were really happy together. They were always going out and doing things, just enjoyed being with each other. The whole thing is just terrible.”

Facebook Twitter Pinterest A survivor is seen walking away from the scene of the helicopter crash. Photograph: Teddy Fujimoto/AP

Udall and Milward were on the trip as part of their honeymoon after getting married last year, according to Udall’s father, Philip, who added that they were trying to book a flight to get to their bedsides. “We have spoken to the hospital and they are in a critical condition, but they told us they are currently stable,” he said.

Barham, the third British survivor, is thought to have been Jason Hill’s girlfriend.

A witness said he saw flames and black smoke spewing from the crash site, heard explosions and saw victims who were bleeding and badly burned. Teddy Fujimoto, a Las Vegas photographer who was doing a wedding shoot near the crash site, said he suddenly saw people running toward the edge of a ravine. He said he heard gasps and went to see what was happening about 600ft (183 metres) below.

“In the gulch there was a helicopter, flames, smoke,” he said. “It was horrible.”

He said that was when two or three small explosions went off in the wreckage and people were not sure what to do. He said some other pilots flying helicopters in the area at the time of the crash descended into the ravine and delivered water and first-aid supplies.

He saw two badly injured women and one of them was calling out a man’s name, he said.

The US National Transportation Safety Board and the Federal Aviation Administration are investigating the cause of the crash. The Hualapai police chief, Francis Bradley, said rescue crews had to fly in and walk to the crash site using night-vision goggles.

“We were hampered by severe weather conditions. We had gusts up to 50mph (80km/h),” he said. “The terrain where the crash occurred … is extremely rugged.” The survivors were airlifted to Las Vegas by about 2am on Sunday, Bradley said.