CHENNAI, August 12: A few private airlines have informally decided at a meeting of the recently constituted Airlines Association of India, formed under controversial circumstances, to hike air fares by about 20 per cent from September this year.The decision of the private airlines to hike the fares appeared to be a pre-planned move. The air passengers have already been burdened with a very high fare level in the domestic sector. Normally, each time Indian Airlines (IA) hiked its fares, the private airlines followed suit. Meanwhile, sources revealed that IA had already planned and budgeted the fare hike well in advance. IA would make out a case that since the private airlines are hiking the fares, the airline would be left with no option.