NEW DELHI: Aviation regulator DGCA took three no-frill airlines to task for allegedly flouting payload restriction norms while flying to Jammu and Patna , where the airports have short runways, and warned them of stopping their operations if they continued to carry full load of passengers.IndiGo, SpiceJet and GoAir were issued notices by the Directorate General of Civil Aviation (DGCA) after the regulator found them violating safety norms by carrying full flights to these two airports where they should fly with 20 per cent less load, official sources said.The regulator, whose officials carried out real-time checks on the flights of these airlines to the two cities, asked the three airlines to report back by tomorrow evening that they would not fly a fully-occupied aircraft.The DGCA, after examining the flight manifests of these airlines for 15 days, found they were carrying 170-180 passengers, instead of 150-155 as laid down in the Standard Operating Procedures (SOPs) for airports with smaller runways.When contacted, the spokespersons for the three airlines refused to comment on the matter.There are strict norms restricting payload for smaller runways to ensure safe and smooth landings. Payload means the total weight of passengers and cargo that an aircraft can carry.Elaborating on the notice, the officials said if the flights to these two destinations are fully booked, the airlines would have to cancel the bookings and curtail the number of passengers to around 150.While IndiGo and GoAir operates Airbus A-320s , which can carry 180 passengers in a full-economy configuration, SpiceJet flies Boeing 737-800s which have a capacity of 189.The Patna Airport's runway length is 6,411 feet, Jammu's 6,755 feet, while the shortest runway in Delhi is 9,229 feet where the two types of aircraft can land with full load of passengers.The officials said these airlines, in particular, were found to have been violating these SOPs almost on a daily basis to earn more revenue but endangering safety.