Can it be " English is everywhere " since everybody breathes the air :)
The pop-up ad refers to teaching English by watching TV programmes. TV programmes are sent via signals that pass through the airways. Notice also that the main site shows a picture of a huge satellite, which is beaming down on areas you can click on to learn more about how to improve your English.
"Air" refers to airways. "English in the Air" means, English is brought to you by satellite feed. English is all encompassing thanks to satellites. :D
They just use terrestrial TV stations, i.e. TVB Pearl and ATV world, which are TV stations assigned to air English programmes. Before 1997 all English programmes are subtitled by Chinese, now they do the same. Because of the complaints of the decline of English among University graduates by business sectors, one influenced person (people) raised the question that English programmes should be subtitled in English about one or two years ago so that the students can follows the dialogues by recording them, so the Government asked the TV stations to subtitle the English programmes in English for the conditions on renewal of their licences. The TV stations had many excuses to subtitle the English programmes in English because they have already subtitled them in Chinese.
So, I think, it maybe under the table, they select some English programmes suitable for youngsters, subtitled them in English and have some quiz about (on?) English on that website with which I have provided.
The phase ‘English in the Airwaves’ is good to me, but it seems to be too
P.S. please keep on correcting my grammatical mistakes or re-phrasing my message so that I can learn!