In 2001, the Hong Kong Aircrew Officers Association (HKAOA) launched a "work to rule" campaign to further its campaign for pay improvements and changes to roster scheduling practices. The action involved pilots refusing to work flights that were not scheduled on their roster. Although this alone did not cause extensive disruption, rostered pilots began to call in sick for their flights. Combined with the work to rule campaign, the airline was unable to cover all of its scheduled flights, and cancellations resulted. Cathay Pacific steadfastly refused to negotiate with the HKAOA under threat of industrial action.[33]