We have never noticed a difference in delivery time for either of them.

Some FCM destinations have longer delivery times than priority.

In any case, when a buyer pays for expedited shipping, using FCM is an invitation for trouble

Most priority is two days, many FC take three. You also get insurance included with priority mail.

It seems to me that Amazon is padding the USPS Priority mail delivery dates. Most everywhere USPS would say 2 or 3 days but Amazon seems to estimate longer than that. I’m starting to wonder if Amazon sees enough USPS packages that miss the 2-3 day delivery window that they just add a buffer to ensure packages are getting there in time for the customers estimated delivery window.

Another thing I wondered is maybe Amazon priority mail isn’t the same as if you bought it from USPS directly? On the labels Amazon prints it will say USPS Priority Mail but on a USPS printed label it will say USPS 2 day or 3 day Priority. That doesn’t seem as likely as my above thought though.

And yeah, to head off all of the contrarian comments, I know we can set our own shipping rates.

But realistically to do so is is to raise the total price for an item high above the competition.

Priority and First Class are the same on Post Office…

Its really a technical difference Priority is in dedicated packaging…but lighter items are called “first class”

USPS estimates 1-3 days domestic delivery for both. My understanding is that first class uses different sorting machines depending on bulk and may use different modes of transportation (priority uses cargo planes), so there may be differences in delivery times, especially over long distances.

They are technically the same, until there is volume at any one point along the way. That’s when Priority will go on the truck, and First Class might get held back a bit.

90% of the time, they will be the same date of arrival, but the odds something goes to 5+ days are far greater with FCM vs. Priority.

No, Priority is usually 2 to 3 days and so is first Class. This is all dependent on a package not getting routed properly or just flat out lost. For the most part they take the same length of time.

Both classes are Air mail. And planes fly at the same speed regardless if they carry first class mail or priority mail.
Difference is only on a ground. Basically when loading the plane they grab first priority mail bins and then first class bins.
If plane is full (the big cart that goes onto plane full) then first class sits and waits for new cart.

But normally there is minimal or 1 day difference in delivery.