Possible actions
First action is to contact the airline immediately by phone or chat and ask for the earliest alternative they can give you on the same ticket. Second action is to check surface options such as a train or long-distance bus that still leave today and arrive at an acceptable time. Third action is to keep the original flight if it is only delayed by a few hours and the rest of the trip can still absorb the shift. Each path needs a quick look at total time and total extra cost before you commit.

Risks
Waiting even one more hour can remove the last seats on later flights or the last tickets on trains. Accepting the first expensive alternative without checking the surface options can cost more than necessary. Leaving the airport without a confirmed next step can make it harder to use any remaining passenger care. Cancelling too fast without knowing the refundable amount can leave you with less money than you expected.

Recommended choice under time pressure
Call or chat with the airline right now and ask for the earliest workable flight on the same ticket. While you are on the line or waiting for the reply, check one train and one bus option in parallel. Take the airline alternative if it gets you there today or early tomorrow without an extreme price jump. Choose the train or bus only if it is clearly faster or much cheaper and still leaves a small buffer. Keep the original flight solely when the delay is short and no better seat exists. Move within the next hour while seats and tickets are still available.

Summary
Last-minute problems reward speed and a short comparison. Contact the airline first, glance at one or two surface alternatives at the same time, then pick the path that limits further damage. The safest and usually fastest move is the earliest same-ticket flight that still works, with a train or bus as the backup if the air options have collapsed. Act before the window closes.