Flight Oslo - Varna prices from €119.37

Aegean Airlines is the largest airline in Greece, operating both domestic and international flights to over 150 destinations. Founded in 1987, the airline has grown to become a major player in the European aviation market, with a fleet of over 60 aircraft and a reputation for high-quality service. Aegean Airlines is a member of the Star Alliance, a global airline network that includes some of the world's largest carriers. The airline has won numerous awards for its customer service, including the Skytrax award for Best Regional Airline in Europe for nine consecutive years.

Air Serbia is the national airline of Serbia, headquartered in Belgrade. It was founded in 2013 as a successor to the former national carrier, Jat Airways. Air Serbia operates flights to over 50 destinations in Europe, the Middle East, and North America, with a fleet of modern Airbus aircraft. The airline offers a range of services to its passengers, including in-flight entertainment, Wi-Fi, and a loyalty program called Etihad Guest. Air Serbia is a member of the Etihad Airways Partners group, which includes several other airlines around the world. The airline has won several awards for its service and performance, including Best Airline in Eastern Europe at the World Airline Awards.

Bulgaria Air is the national flag carrier airline of Bulgaria, headquartered in Sofia. It operates scheduled flights to over 20 destinations in Europe, the Middle East, and Africa. The airline was founded in 2002 and has a fleet of 10 aircraft, including Airbus A319s and Embraer E190s. Bulgaria Air offers both economy and business class seating, as well as a frequent flyer program called Fly More. The airline has codeshare agreements with several other airlines, including Air France, KLM, and Alitalia. Bulgaria Air is a member of the International Air Transport Association (IATA) and the Association of European Airlines (AEA).

Lufthansa is a German airline and one of the largest airlines in Europe. It was founded in 1953 and operates flights to over 200 destinations worldwide. Lufthansa is a member of the Star Alliance, which is the world's largest airline alliance. The airline has a fleet of over 300 aircraft, including Airbus and Boeing planes. Lufthansa offers a range of services to its passengers, including in-flight entertainment, Wi-Fi, and a frequent flyer program called Miles & More. The airline is known for its high-quality service and has won numerous awards for its customer satisfaction and safety standards.

Wizz Air is a low-cost airline based in Hungary that operates flights to destinations across Europe, the Middle East, and North Africa. Founded in 2003, the airline has grown rapidly and now operates a fleet of over 100 aircraft, serving more than 150 destinations in 44 countries. Wizz Air is known for its no-frills approach to air travel, offering low fares and charging extra for additional services such as checked baggage and in-flight meals. The airline has a strong focus on efficiency and cost control, allowing it to offer some of the lowest fares in the industry.