Ward Powers referred me to The Books and the Parchments ... a great book for
a rationale behind this pronunciation.
He also pointed out that this means that every letter and combination has
its own sound, making it easier to hear what characters are being used in
spoken Biblical Greek.
When I went to college [20 OUCH years ago] we got A as in MATE [not the
aussie way!] from Wenham and E as in EEK a mouse! from Jay in 2nd year.
Here is a quote from a private post Ward sent me. I found it very
interesting.
F F Bruce (in The Books and the Parchments, p.18) says, '... and so H (eta)
was used to represent a long open "e" sound, similar to the "ea" in English
"bear".' See the full quotation from Bruce in Footnote 5, on pages 308-309
of my book. I reckon F F Bruce knows his stuff. That's one reason why I go
with the "AIRTA" pronunciation.
Secondly, H is a long E (epsilon). Try saying E, and then make it long,
i.e., continue the sound, and what do you get? What you get is not anything
like EIGHTA or EATA. For my money, you get AIRTA.
Thirdly, we have good reason for taking the pronunciation of iota as "ee"
as in "ski" or "kiosk"; and equally good reason for taking the epsilon-iota
diphthong as pronounced as in "eight", "rein", "veil", etc. So if we were
to use either of these pronunciation for HTA, we would have two differing
vowel sounds pronounced the same, for no good reason (unless of course we
avoided this by finding other pronunciations for iota and epsilon-iota -
which would then cause other complications; Jay (pages 4-5) pronounces iota
when long, and EI, both the same as AI; Wenham (page 20) pronounces H and
EI the same: confusing). To the greatest extent possible, a pronunciation
scheme should be phonemic, that is, one sound/one letter, so that if you
can SAY the word you can also SPELL it. This significantly helps students
(indeed, everyone using the language).