Analysis of information sources in references of the Wikipedia article "General Dynamics F-16 Fighting Falcon variants" in English language version.
To bring the existing F-16As closer in capabilities to the F-16C a major modification programme led to the Block 15 MLU, often designated F-16AM. The M is this case stands for Mid-Life Update (MLU). Sometimes, these MLU upgraded F-16s are referred to as Block 20, but these are only new aircraft (see next paragraph). [. . .] Block 20s were newly built F-16As for the Republic of China Air Force. These are externally the same as the Block 15 MLU
The Mid-Life Update (MLU) version of the F‑16B Block 15 is called F-16BM [. . .] Block 20 is an externally very similar version, for the Republic of China Air Force.
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: CS1 maint: location missing publisher (link)With the expected completion in 2023 of upgrades to Taiwan's existing 142-strong fleet of F-16A and F-16B fighter jets, the island expects to have a total of 208 F-16Vs by 2026, reports said.