NEW DELHI: For the first time since 2008, India's busiest airports - Delhi and Mumbai - have seen a year-on-year dip in passengers in 2019 compared with 2018. While Indira Gandhi International (IGI) Airport saw fewer domestic passengers, Chhatrapati Shivaji Maharaj International Airport (CSMIA) registered a fall in both domestic and international carriage.Amid an overall slowing economy , the biggest reason for decline was Jet Airways' collapse last April. IndiGo and GoAir's Pratt & Whitney (PW) engine troubles for their Airbus A320 Neos and SpiceJet's grounded Boeing 737 Max too contributed to fewer flyers last year. Closure of Pakistan airspace for 138 days led to airlines cancelling flights to and from Delhi and Mumbai for varying durations. As a result, Delhi and Mumbai were deprived of the records they were hoping to achieve in 2019.IGI, India's busiest airport, was just 2 lakh short of the magic 7-crore annual passenger (domestic-cum-international) mark in 2018 when it registered 6.98 crore flyers. DIAL's provisional data for 2019 shows it handled 6.8 crore passengers - down 2.6%.Delhi airport saw 1.9 crore international flyers in 2019 , up 0.6% from 1.8 crore in 2018. Domestic flyers, however, fell 6% from almost 5.2 crore in 2018 to 4.9 crore in 2019. Similarly, CSMIA had ended 2018 two lakh short of the 5-crore (domestic-cum-international) flyer mark at 4.98 crore. But Mumbai International Airport Ltd (MIAL) data for 2019 shows it handled 4.7 crore passengers - down 5.6%.Mumbai airport saw 3.38 crore domestic flyers in 2019, down 3.4% from 3.5 crore in 2018. And international flyers fell 7% from 1.4 crore in 2018 to 1.3 crore in 2019. The last time domestic air travel had dipped across India, say airline officials, was in 2008 when the global slowdown started but thanks to low cost carriers quickly spreading their wings in India, that issue was overcome from 2009 onwards.While IGIA and CSMIA were Jet's twin hubs in India and suffered the most from the airline's collapse, India as a whole did not see a fall in number of air travellers. DGCA data for the full year 2019 is awaited. Its January-November data shows the country saw 13.1 crore domestic flyers in 11 months of 2019, up almost 4% from 12.6 crore in the same period of the previous year. DGCA's January-June data shows India saw 3.19 crore international passengers in the first six months of 2019, up 1.2% from 3.15 crore in the first six months of the previous year.AAI saw a modest 5% growth to 14.8 crore domestic-cum-international passengers in January-November 2019 at its airports (not JV metro ones) over 14.1 crore in the same period of the previous year. However, these are a far cry from the double digit growths seen in past few years. Bengaluru and Hyderabad are yet to share their 2019 passenger numbers.DIAL said in a statement: "….technical issues in aircraft engines (referring to PW engine trouble of A320 Neos)/newer aircrafts (referring to B737 max) impacted supply side of air traffic . During CY 2019, Indigo, SpiceJet, and GoAir faced issues on grounding of their aircrafts by the regulator due to technical issues leading to cancellation or lower operations impacting air traffic."