The three -- Gulbag Singh, Davinder Singh and Iqbal Singh -- had boarded the plane in Sacramento on November 15 after being cleared by the security.

In a complaint letter to the Airways, 'United Sikhs' protested the incident and warned it of legal action unless prompt amends are made.

The group pointed to the severity of the racial profiling and discriminatory treatment, sought an apology and compensation for the three and offered training for US Airways staff.

The three, who had boarded the plane for Salt Lake City, Utah, were sitting together in the rear of the aircraft, in their assigned seats.

After having been on the plane for approximately ten minutes, they were approached by one of the ticket-reception desk workers and asked to exit the plane.

While none of the three could adequately comprehend or speak English, the group complied and exited the aircraft, the United Sikhs said.

When it became apparent that the group was unable to converse with US Airways representatives, a Punjabi interpreter was called to assist, it said.

The interpreter informed Iqbal Singh, on behalf of the US Airways representatives, that the pilot was refusing to fly if they were onboard the aircraft, it added.

When Iqbal Singh asked why, the US Airways representatives were unable to give a clear answer, and the interpreter went on to persuade the three not to raise any objection because it could lead to more problems, the organisation said.

The trio, having become concerned, fearful, and worried about what had happened, took the only option they were given, which was to stay the night in a hotel and depart on a Delta Airlines flight the following morning to Salt Lake City, it added.

Terming the treatment "discriminatory and publicly humiliating", Gulbag Singh said, "I would like to ask the average American to think about how they would feel if they were cleared by security, were sitting on their plane, and then were asked to leave for no good reason. It is ridiculous that a person should be submitted to such second class treatment."

"Sikhs will not stand to be discriminated against. There is no satisfactory justification for US Airways to treat people in this way. This is a clear violation of civil rights and they must take immediate actions to address this issue," said Harpreet Singh, Legal Director of United Sikhs.

In a separate incident on November 17, 2008 at Logan International airport in Boston, it said, one Jaspal Singh was sent to secondary screening where he was subjected to humiliating treatment when a Transportation Security Officer roughly searched his turban, almost untying it.