NATO is moving quickly to admit Sweden and Finns after they applied to join.
Both countries have close relationships with the military alliance.
NATO leaders think the two countries bring immediate benefit.
The alliance's close relationship with the Nordic countries was on full display in the skies over Northern Europe in June.
The British, French, German, Norwegian, and Belgian air forces took part in a drill with their Swedish, French, German, and Norwegian counterparts.
The purpose of the exercise was to show the ability to conduct complex air operations over long distances.
The chief of the Norwegian air force said it was the first time they had conducted such an advanced exercise with NATO and partner nations.
The militaries of 14 NATO members, including the US, joined from June 5 to June 17 Over 45 ships, more than 75 aircraft, and thousands of personnel were involved in the 51st iteration of the maritime focused exercise.
During one drill, a US Air Force KC-135 tanker refueled US, Finnish, Swedish, and German jets.
NATO's air component and deterrence in the north will be strengthened by the June exercises which demonstrated the strong relationship Finland and Sweden have with their NATO neighbors.
The fleet of 55 McDonnell Douglas F/A-18C Hornets is owned by Finland. The single-seat F/A-18C can switch between fighter and attack configurations in less than a minute. It has seen combat in North Africa, the Middle East, and the Balkans, as well as being operated by the US Navy and Marines.
The Ministry of Defense said that the Hornets will be retired by the year 2030. The first F-35 is expected to be delivered by the year 2026.
The F-35A is gaining popularity among US allies. The stealth jet can be used to enhance the effectiveness of air and ground forces.
The only fighter jet in Sweden is a domestically designed and built aircraft.
The Gripen doesn't have the stealth of an F-35, but it's a reliable and cost-effective aircraft that brings a number of important capabilities into the fight.
The gripen can be used in many different ways. Hollings said that its small size allowed it to take off and land on austere airstrips or highways while carrying air-to-air weapons.
The Swedish jet is one of the few fighters that can maintain supersonic speeds without burning fuel. It increases an aircraft's endurance at supersonic speeds by decreasing its fuel consumption.
The US-made F-22 is the only jet that can fly fast. Russia's jets don't have the ability.
The program has had controversy, Hollings said, but it was designed to be easy to fly, inexpensive to maintain, and quick to upgrade, and that makes for a handy jet to have around in a fight.
The Swedish jet has been used in exercises. The first day of a major US-led exercise in Alaska in 2016 it scored 10 kills against peer aircraft, including a 4.5-generation Eurofighter Typhoon.
70 Gripen Es, an upgrade over the -C model, will be delivered by the end of the century.
It will be difficult to integrate two air forces with a combined fighter fleet of 126 aircraft into NATO operations.
Tactical integration is achieved through frequent joint exercises because the F/A-18C and the Gripen are both used by other NATO members.
Hollings told Insider that mixing national air forces and platforms is always a challenge. A mix of aircraft is a potent tool in a large-scale fight.
NATO will have a tactical advantage if the number of aircraft is increased.
Hollings said that fighter pilots want to play to the strengths of their own aircraft and the weaknesses of their opponent. You really complicate the combat calculus for your opponent when you head into a fight with a variety of fighters at your disposal.
NATO leaders are eager to have Finn and Swedish forces in the alliance despite the fact that they won't have the advanced jets.
The Finns and Swedes will bring "quite a bit of capability and capacity to the alliance from Day One," Gen. Christopher Cavoli said during his nomination hearing in May.
From a military perspective, I look forward to the accession of the two Nordic countries.
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