The union that represented most of the Honolulu Airport baggage screeners disciplined for improper screening said it plans to appeal almost all the cases.

The Transportation Security Administration said Friday it has fired 28 employees and suspended 15 others after its investigation into improper screening of checked baggage at Honolulu Airport. Three employees resigned or retired. There was no information on two remaining cases.

The American Federation of Government Employees claims it won reductions in the severity of discipline for “six to eight” of the officers, either reducing a firing to a suspension or reducing the period of suspension, union general counsel David Borer said.

The union argues that the front-line workers should not be punished for what it claims was the fault of management. Five TSA managers were let go in June when the investigation was made public. Among the fired managers were Glen Kajiyama, who was federal security director, and William Gulledge, assistant federal deputy director for screening.

“You’ve got top TSA executives there who have been fired or moved out as a result of this whole incident,” Borer said. “The agency still persists going after the guys who were basically just taking orders. They were under a lot of pressure from the airlines and management to move these bags faster.”

TSA officials have declined further comment on the disciplinary measures, citing that the cases are all personnel matters.

The union represents 32 of the 48 cases. Borer said the union plans to appeal all 32 cases, except for two employees who have sought private counsel.

“First we challenged the proposed disciplinary action, and now we’re appealing the actual discipline,” Borer said.

The employees have 30 days after they receive a letter of disciplinary action to file an appeal with TSA. The agency faces no deadline in deciding the appeals.

The investigation began at the end of last year. Allegations surfaced in December when two TSA employees reported that luggage was allowed to go on flights without being screened or checked for explosives.

The alleged misconduct affected a “limited number” of daily flights during the last few months of 2010, the TSA has said. The workers were stationed at Lobby 4 of the airport, which services 12 airlines.