Airlines must ensure that all check-in counters at the Delhi airport are fully staffed to minimise passenger inconvenience as smog has started affecting the flight operations, Aviation Minister Rammohan Naidu directed on Wednesday.The minister gave this direction during a meeting with representatives of major airlines, Delhi International Airport Limited (DIAL), officials of the Ministry of Civil Aviation, Directorate General of Civil Aviation (DGCA) and the Bureau of Civil Aviation Security (BCAS).