It appeared on the cover of the January 1975 "Popular Electronics" magazine with an article (probably) by Leslie Solomon. Leslie Solomon was an editor at Popular Electronics who had a knack for spotting kits that would interest people and make them buy the magazine. The Altair 8800 was one such. The MITS guys took the prototype Altair to New York to show Solomon, but couldn't get it to work after the flight. Nonetheless, he liked it, and it appeared on the cover as "The first minicomputer in a kit."
Solomon's blessing was important enough that some MITS competitors named their product the "SOL" to gain his favour. Some wags suggested SOL was actually an abbreviation for the condition in which kit purchasers would find themselves.
Bill Gates and Paul Allen saw the article on the Altair 8800 in Popular Electronics. They realised that the Altair, which was programmed via its binary front panel needed a high level language. Legend has it that they called MITS with the claim that they had a BASIC interpreter for the Altair. When MITS asked them to demo it in Albuquerque, they wrote one on the plane. On arrival, they entered the machine code via the front panel and demonstrated and sold their "product." Thus was born "Altair BASIC."
The original Altair BASIC ran in less than 4K of RAM because a "loaded" Altair had 4K memory. Since there was no operating system on the Altair, Altair BASIC included what we now think of as BIOS. It was distributed on paper tape that could be read on a Teletype. Later versions supported the 8K Altair and the 16K diskette-based Altair (demonstrating that, even in the 1970s, Microsoft was committed to software bloat). Altair BASIC was ported to the Motorola 6800 for the Altair 680 machine, and to other 8080-based microcomputers produced by MITS' competitors.
[Forrest M. Mimms, article in "Computers and Electronics", (formerly "Popular Electronics"), Jan 1985(?)].
[Was there ever an "Altair 9000" microcomputer?]