First, America has to rejoin JCPOA. Then Iran has to agree to meet the conditions of JCPOA again. Once those two things have happened and IEAE inspections of Iran’s nuclear facilities resume and once Iran is seen to be sticking to the agreement, then America should start easing sanctions. Once those sanctions start being eased, Iran may be in the position to consider placing an order for Boeing planes.
I'm not sure there is a method in the JCPOA for America to rejoin; and I think your concept is along the line of wishful thinking.
The reality is the USA formally withdrew from the JCPOA, and no longer has any say in it. Former President Trump wanted for America to go it alone.
Now, President Biden's Administration might be in a position to ask Iran to come into compliance with the JCPOA as part of a condition for easing the restrictions that the USA unilaterally applied under President Trump; and it might be something less.
Keep in mind that by all reports Iran was well in compliance with the JCPOA when President Trump withdrew and imposed much stricter sanctions. Why should Iran believe that compliance with the JCPOA is to their benefit after that.
At least the aircraft gives a starting point for a discussion... I am quite sure that Iran knows that at least parts of compliance with the JCPOA will likely be required. But, at this point I belive that USA is likely forever no longer a part of it. I would like to point out - that Iran would likely have to approve along with all other parties if there is even a legal way for the USA to be a legal part of the JCPOA.
The real question for the USA... is how to move forward working outside of the JCPOA, as the USA is outside of it already.
Have a great day,