I may need to write a how-to for Canadians travelling to the States. I needed to get an antigen COVID-19 test to fly into the States. It had to be administered within 72 hours of my departing the country. I got a check-in counter guy at the airport who said that it was 24 hours. He was wrong after consulting with a colleague.
With the recent changes by the US administration, this check-in counter guy is now correct. It's now 24 hours. It means that for my next trip, I'm taking my antigen test hours before I board my flight. It all works out fine. I have booked my appointment.
To get into Canada, I need to do a PCR or molecular COVID-19 test 72 hours before boarding my flight in the US heading back home. I actually did a NAAT test at a local CVS pharmacy. I got to self-administer the test at the drive-thru and drop my swab in a tube in a special box. I got my results in just over a day. It was also free. Had I done a PCR test at the airport, it would have cost me $200 USD.
I am glad that everything worked out. I fly again in over a week, so I'm more comfortable now with the experience that I have gained.