Omega Aerial Refueling Systems is the world's first commercial company providing air to air refuelling services for aircraft. Omega tanker planes are remodelled Boeing 707 planes, now called KC-707 and old Douglas DC-10 planes, now called KDC-10. Omega's customers are US army and US Navy air forces as well as partnering countries' air forces, but Omega is not part of the army, but a commercial enterprise performing a pay by the hour service. Some of Omega's aircraft can fly 1200 hours without landing.
This is an Omega KDC-10 tanker, a former Mc Donnel Douglas DC-10, now heavily rebuilt. Here they are used in air to air tanking exercises of for example Finnish Air Force F/A-18 fighter planes and in Nato's air strike exercises.
Picture from Helsinki-Vantaa airport in Finland 12.5.2018 by Ilkka Siissalo.

Another view of the Omega tanker KDC-10 registered as N974VV.
Picture from Helsinki-Vantaa airport in Finland 12.5.2018 by Ilkka Siissalo.

Antonov An-2 is a Soviet mass-produced single-engine biplane utility/agricultural aircraft designed and manufactured by the Antonov Design Bureau beginning in 1946. Its remarkable durability, high lifting power, and ability to take off and land from poor runways have given it a long service life. The An-2 was produced up to 2001 and remains in service with military and civilian operators around the world. (Text from Wikipedia)
Picture from Skopje, Macedonia 28.10.2018 by Ilkka Siissalo.

This is a Piper PA-31-310 Navajo, register LN-NPZ owned by Blom Geomatics. The company says it is used for aerial survey and photos. The company has three similar Navajos.
Picture from Trondheim Værnes airport in Norway 20.10.2018 by Ilkka Siissalo.

This Beech King Air B200 is one of the ambulance planes used in Norway. Norway is a country with difficult terrain and ambulance flights and helicopters are often needed. Ambulansetjenesten can have over 8600 ambulance flights per year using planes such as this Beech King Air B200. Mostly they are needed for transportation of passengers between two different hospitals.
Picture from Bergen airport 28.3.2019 by Ilkka Siissalo.

The ambulance plane seen above has just landed and has here just taken its parking position. Doors are opening and a normal ambulance is waiting for the patient to take him or her to the Bergen university hospital.
Picture from Bergen airport 28.3.2019 by Ilkka Siissalo.

Here the patient is being quickly hurried away from the plane into the waiting normal ambulance.
Picture from Bergen airport 28.3.2019 by Ilkka Siissalo.

This is an old McDonnell Douglas DC-10 which has been converted into a flying private eye clinic for orbis.com.
Picture from Los Angeles airport (LAX) 26.10.2016 by Ilkka Siissalo.

This plane caused a "What the f*" reaction. I was staying at the Icelandair hotel by the Reykjavik City airport with full view from my hotel room window to the plateau of the airport and I was already sleeping as I heard some really big plane coming. I got up - and the reaction - "What the...". Clothes on and quickly outside. This is a World War II time DC-3 or actually its military version Douglas C-47 freighter built in 1942 for the US army for the purpose of invasion of Normandy. An then much, much later it has received new wings, modern turboprop engines and a new "nose" with very special equipment. It is now after the modification called Basler BT-67 and it is owned by the Canadian company CGG. It's a very special machine used for finding oil fields under the sea. I heard its crew cursing their job as they said, youngsters are treating them as criminals when they search for oil in the arctic regions, but the work itself is science, and a very difficult field of science. They had flown that day for well over 10 hours very low above the sea level from a very small airfield in the Inuit region of Northern Canada to Reykjavik.
Picture from Reykjavik City airport 13.1.2018 by Ilkka Siissalo.

The same C-47 / Basler BT-67 as above.
Picture from Reykjavik City airport 13.1.2018 by Ilkka Siissalo.

What is today N850SD is a Cessna 208 Grand Caravan from the year 1997. It was first registered in Sweden and flew there in private use for a number of years, but then it was sold to the US where it went through a thorough modification. Its fuselage was elongated and it received broadly opening new doors as it became a specially for skydiving fitted special plane and it is now a "Cessna Grand Caravan with Blackhawk conversion". One of the newest web pages mentioning the plane was offering it for sale in USA. But here we see it still used by a US skydiving group and being refuelled at the Reykjavik City airport in Iceland.
Picture from Reykjavik 12.1.2018 by Ilkka Siissalo.

A detail of the same plane N850SD showing the logo of Blackhawk, which made the conversion to elongate this Cessna and fit it with a stronger engine and gear needed for skydiving.
Picture from Reykjavik City airport in Iceland 12.1.2018 by Ilkka Siissalo.

This is a Bombardier CRJ200 commercial jet, which was last used in Lithuania. It was flown to Helsinki-Vantaa airport on the 16th of December 2020. That was its last flight. It is now used by the vocational school Varia owned by the city of Vantaa. Varia trains future airplane mechanics and aviation electronics specialists.
Picture from Helsinki-Vantaa airport 9.1.2021 by Ilkka Siissalo.