Getting attention is what is important.
The primary purpose of using MAYDAY, PAN or SECURITE, is to secure the
attention of all others on the r/t channel, in two respects.
1. You need to talk to those who may be able to help you.
2. You need everyone else to stay quiet while you talk to those who
can help you.
No other phraseology will achieve both purposes INSTANTLY.
No other phraseology will ENTITLE you to priority on the channel.
And it should work EVERYWHERE. It is called ' The International Code of Signals.'
'Houston, we have a problem' will not cut through the crap on a busy
r/t channel.
I'm not a pilot, but I was a Marine Radio Officer for some years, and to the best of my knowledge the rules are the same.
The three codes are only a broad indication of the severity of the problem.
A Mayday can be downgraded to a PAN, or cancelled, if appropriate..
To illustrate: While at anchor in Table Bay, Capetown, some years ago,
we had a fire in the Engine room. Fire bells went off, I went to the Bridge
to see whats up. The Captain was screaming ' Capetown Radio, Capetown
Radio, emergency XXXX on fire" etc on VHF Channel 16 (emergency and calling channel), and getting drowned out by everyone else on the busy
channel, thus no response.
A single call of SAYKURITAY, SAYKURITAY, silenced the channel instantly
and got the undivided attention of Capetown Radio.
That's the way it is supposed to work.
So if you want to be all girly and coy, by all means do so, but dont be
surprised if no-one appreciates your plight.