1971 - 1980

In June 1971, the West German airline Lufthansa opened a regular cargo line to Frankfurt.  Boeing 737 aircraft, which were especially adapted for transportation of container and palettes, used this line once a week. 
Brnik was also the first airport in this part of Europe capable of receiving and dispatching cargoes by palette.

After expanding the runway and increasing the length of the taxi path to 2200 metres, a wide-fuselage DC-10, ran by the American Trans International Airlines, landed at the airport in June.

The summer season of 1974 meant a severe test for the new passenger terminal and other new buildings.  After thorough checking by several federal commissions, Brnik airport took over the traffic from Zagreb airport as it was being renovated that summer. The traffic density increased tremendously.  Airplane and passenger traffic was almost doubled.  In 64 days, a total of 2670 airplanes arrived and left, more than 45 per day, bringing 287,447 passengers and 1853 tons of cargo.

In 1975 the traffic structure changed. Domestic traffic increased, although in absolute numbers it did not exceed international traffic. The ratio between national and foreign airlines changed in the favour of national airlines.
Total traffic was less than the year before, but nevertheless exceeded the traffic for 1973 easily: 553,000 passengers compared to 368,000.

The increase in cargo traffic required the building of a new customs building of 6000 m2.

After more than a years preparations, on the night of 30 June 1978, at midnight, the airport was shut down for thorough reconstruction.
The renovation included bringing the runway up to modern standards and increasing it to its current size, 3300 x 60 m.  At the same time, the building was redone, the power supply was improved and the surroundings were adapted to meet the standards for CAT II category.
During this time air traffic was redirected to Maribor and Pula, whereas the intercontinental line was redirected to Zagreb.
A longer runway and its higher capability enabled a direct intercontinental line without any stopovers.  On 20 December 1978, JAT began flights to New York, using DC-10s. A regular connection with the USA was introduced as early as April of that year.  However, only the new runway enabled landings and takeoffs with a fully loaded DC-10 on an intercontinental line.

The reconstruction of the airport and updating of the runway enabled the airport to acquire an ICAO licence, category II, for landings and takeoffs in bad weather conditions.