So here is Belgium ... 10 airbases, including the 5 operational bases during the late Cold War, a few reserve/dispersal fields (could've added 5-6 more), a transport base and a POMCUS site with associated airfield. Enjoy and next, on to France!
Beauvechain AB: Beauvechain AB is a current base flying the 1st Wing flying Helos. Between 1979-1996, the 1st Fighter Wing was here, flying 48 F-16's in two squadrons.
Chievres AB: Currently the main airfield for SHAPE HQ and also attached to the 86th Airlift Wing out of Ramstein AFB in Germany. Prior to this, it was home to the now disbanded 7th Fighter Wing of the Belgian Air Force. It is a current base with a heavy US presence. It could clearly accommodate at least a couple squadrons of warplanes in an emergency, although ammo is guessed at.
Florennes AB: Home to the 2nd Fighter Wing with F-16's. During the end of the Cold War, it also served as a base for 48 GLCM's. I have gone ahead and added this (as well as a notional company of US Marines) so if your scenario is from before or after their deployment you'll want to remove them.
Jehonville AB: A reserve/dispersal airbase in the Ardennes. While it has no permanent units attached it can accommodate a squadron if need be. There is an immense ammo field to the northeast, just off the edge of the runway oddly. I chose not to include this as I'm assuming it's not really meant for the airfield.
Kleine-Brogel AB: An airbase on the Dutch border, it is home to the 10th Fighter Wing, flying F-16's and reputedly home to at least 20 B-61 nuclear weapons shared with the US.
Liege AB: A civilian airport, in the late 1980's it was home to the 3rd fighter wing, flying 36 Mirage V's and 22 recon versions. Also known as Bierset AB or Bierset-Liege AB.
St. Truiden AB: St. Truiden (or Sint-Truiden) AB is a former Belgian airbase, closing in the 1990's and transitioning to civilian use. In the late 1980's it was a training base flying 32 Alphajets of the 9th Fighter Wing in the training/attack role.
Ursel AB: A field in Western Belgium, it served as a dispersal airfield with minimal facilities. It can accommodate a few planes but is a small base.
Weelde AB: A reserve airbase, stores numerous retired aircraft such as older F-16's.
Zutendaal AB: A reserve airbase in the far east of Belgium, it also appears to be a former POMCUS site. According to Any Johnson's OOB, the US 1st Cavalry Division was supposed to draw it's equipment from here. Today it still serves in a similar roll.
Fun facts about Belgian Air Base. It was pretty common to let civilians use the airfields as well, mainly on the weekends (more frequently for the reserve airfields). I only mention this as it might make a battle involving Belgian airbases more interesting should you choose to include them.