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About two months ago I applied for an internship at a company and was asked to complete an online programming test. I passed the test and they followed up with a phone interview a few days later, which I thought went well. I didn't hear from them at all for nearly a month (I thought I didn't make it past this stage). However, about a week ago I got a call from one of the recruiters, and he mentioned that I had made it to the final interview stage, which involves flying over to their offices and completing various tasks over an entire day. He then asked me to email a list of days on which I would be available for the interview, which I did. He replied to my email later that day asking whether I would be available on any other days, as it would be unlikely for them to guarantee an interview on the days I specified. I quickly replied with a few more days on which I'd be available.
It's been nearly four days and I haven't received any reply yet. Should I send a polite email asking about the status of my application, or just give it some more time?