Passengers headed to Hawaii had to make an unscheduled stop in California after the bathrooms on a United Airlines flight reached full capacity.

Flight 1219 was supposed to be a direct flight Sunday morning from Denver, Colorado to Kauai, but about five hours into the trip the pilot announced that they were being diverted to San Francisco.

The issue was apparently because the toilets were not serviced in Denver before takeoff.

A United Airlines flight from Denver to Hawaii was diverted to San Francisco on Sunday because of issues with the bathrooms (file image)

Passengers were told that the toilets had not been serviced in Denver and they were full to capacity (file image)

'Everyone was disgusted,' passenger Rich Anderson told Fox 31.

Anderson, who was heading to Hawaii to celebrate his wedding anniversary with his wife Kristin, said they were halfway over the Pacific Ocean when the announcement was made.

'We were probably three hours from Hawaii and they announced that the toilets were all full,' Kristin Anderson said.

Once the plane landed in San Francisco, passengers were put on another aircraft. What was supposed to be an eight-hour flight turned into a 16 hour one.

'The pilots failed,' Anderson told the outlet. 'They didn't do their job. This should not have happened. This was human error. There was no act of God. There was no weather. This was just human error.'

Anderson said the bathrooms were a problem early into the flight. He told Fox 31 that when he first tried to use one, it was locked.

'I had gone back partway through to the bathroom and one of them was locked,' he said. 'The flight attendant said that one is not working. I think they were locking them as they were filling up.'

United Airlines apologized for the inconvenience by offering travelers 10,000 bonus miles or a $200 travel voucher.

United Airlines apologized by offering passengers 10,000 bonus miles or a $200 travel voucher (file image)

'I am very sorry that our lavatories had reached capacity while Flight 1219 was en route to Lihue,' the airline said. 'A decision was made to turn back and land in San Francisco where arrangements were made to to change planes. I can appreciate that this experience was disappointing and unpleasant.'

Anderson, however, isn't happy with the company's apology and said United Airlines ruined vacations for a lot of people.

'They gave us a really crummy start. There were a lot of elderly people and people with little tiny kids,' he said.

The airline did not say why the planes weren't serviced before takeoff.