It's a Tuesday, so the numbers will be much smaller than yesterday or next Friday.

Here's an educated wild-... guess:

250,000 in the USA plus another 500,000 worldwide for a total of 750,000 people in the air at this moment.

Out of 6.333 billion people worldwide, 750k is not very many. But then again, total daily passengers worldwide may equal 4 or 5 million people. Not insignificant.