You would use the same pattern to ask whether anything was 'here', so it is very useful to learn it:
- Oes meddyg/teigr/siop/oriel/banc/cwdyn o aur/garej/parti yma? - Is there a doctor/tiger/shop/art gallery/snake/bank/bag of gold/garage/party here?
You have also now learned the word for 'an aeroplane'.
If you're waiting in an airport for a plane, a slight variation of this phrase:-
Oes awyren yma eto? = Is there a plane here yet?
would be a more natural and concise way (in Welsh) of asking if an expected plane has arrived than the more literal translation from English.
ie, Ydy'r awyren wedi cyrraedd eto? = Has the plane arrived yet?
You could ask Oes athro yma? "Is there a teacher here?"
But it would be unusual to ask "Is there a Sioned here?" -- you would generally have a specific Sioned in mind, rather than being satisfied with anyone who happens to be called Sioned.
And then you need Ydy Sioned yma? since Sioned is specific. Much as you would ask Ydy'r athro yma? for "Is the teacher here?" (with a specific teacher in mind, "the teacher" rather than "a teacher").