The English translation in the subtitles makes much more sense: "At least they could make an announcement", but I don't understand how the German sentence meant that.
This is not easy as the sentence makes heavy use of idioms. Let us work through it step by step, but keep in mind that synchronisations (and subtitles) are often quite losely based on the original:
Jetzt können sie langsam auch mal was sagen.
First, who is "sie"? Here it is the "impersonal 3rd person plural". "Sie" means "the organisation [I am dealing with]", for instance:
Sie haben meine Steuern erhöht.
The "sie" here could mean the IRS, who found out you have to pay more taxes or maybe the government, which increased the tax rate, etc.. It doesn't mean a certain group of people in particular but rather the organisation (whichever it may be) as a whole.
Here, by "sie" the speaker means the airport and its administration, whoever it is who could make some announcement should do so by now.
What means "auch mal"?
The "mal" is a shortening of "einmal", but that doesn't make it any clearer perhaps. You use this phrase similarly to the English "for a change": you deal with a situation which has been like this for a while (here: no announcements made) and you think that it is time for such a change.
Here is an example: we want something from a third person and we talk to that person. That is: you argue the whole time and I remain silent. So at some point you turn to me and say:
Sag doch auch mal was!
That is: "Say something too, for a change".
"Langsam": This is probably the hardest one. The direct translation is "slow" or "slowly" but that doesn't explain the meaning. It is ironical and means the exact opposite: something, which should have happened already, should happen and rather sooner than later. The best English translation is perhaps "being high time": I have waited for something to happen long enough and now I am quite anxious for it to happen.
Coming back to the example before, adding "langsam":
Sag doch langsam auch mal was!
would add some urgency to the command: not only should I change my course of action and say something but it is also high time for doing so.
So, the translation is basically: they (the airport) should make an announcement (instead of being silent) and it is about high time for doing so.