Pula's tiny Istrian airport sees no direct widebody service from the US, so anyone booking business class from Denver to Pula is really booking a two-leg journey through a major European hub, with connections built around Lufthansa, Turkish Airlines, or Croatia Airlines completing the final short hop. The most reliable routing I've flown repeatedly runs through Frankfurt or Munich on Lufthansa, where DEN-FRA nonstop service puts you into position for a same-day connection onward, sometimes via Zagreb on Croatia Airlines rather than direct into Pula, since Croatia Airlines' Pula service is heavily seasonal and skews toward summer leisure demand. Turkish Airlines offers an alternative via Istanbul, and their long-haul business cabin on the 777 and A350 fleet remains one of the more generous hard products flying into Europe, with lie-flat seats and a dine-on-demand service that makes the extended connection feel less punishing.
Lufthansa's transatlantic DEN-FRA sector is where the real seat selection matters: depending on aircraft assignment, you'll find either the older fully flat business seat or, increasingly, the newer Allegris cabin now rolling out across the long-haul fleet, which offers more privacy with sliding doors on select subfleets. My advice from having connected through Frankfurt more times than I can count: build in at least two hours there even with a confirmed itinerary, since FRA's non-Schengen transfer process for onward EU flights can eat time unpredictably, and Lufthansa's business lounges in Terminal 1 are worth the walk for a proper sit-down meal before the short Croatia Airlines or connecting flight.
Shoulder season—April, May, September, and October—consistently delivers the best value on this itinerary, both because Istrian tourist demand collapses outside peak summer and because transatlantic business fares from Denver soften once the ski season traffic fades. Given the multiple carrier combinations and routing options into Pula, setting up fare alerts across Lufthansa, Turkish, and Croatia Airlines is the smartest way to catch a favorable business class fare before it disappears.
