"Alignment" and "equivalence" are legal terms. Alignment actually means that you have to align your laws to those of the leading body (the EU in this case) with no divergence possible. Which of course would mean that the UK would have to incorporate EU law without any input to it, quite difficult in any case, and especially in this one. Equivalence means, that the individual legal approach of one country is deemed sufficiently equivalent to another that it allows to accept that set of laws to be equivalent, while not being the same. That happens between the EU and the US for example in quite a few areas (over 150 agreements between the EU and the US do exist today). However, equivalence can be cancelled by either side unilaterally with just 30 days notice, unless otherwise safeguarded. It needs constant work and consultation and is extremely labour intensive on the regulatory side for both parties.
That said, i haven't seen any statement of the EU (council or commission) that expresses any wish to keep the UK in EASA, just a preparatory notice that the EU would be willing to assume equivalence for the first few moments after a disorderly brexit, provided that the UK reciprocates, however, that is just an opinion for now and does not constitute a legal framework. As a "no deal" or rather disorderly brexit would become apparent a few weeks before brexit date, that could be hardened in emergency negotiations on that topic, however, for that it will compete with other stuff like medical transportation etc. as for example the UK cannot produce enough insulin on its own to keep its diabetics alive, most is imported from the EU. Air travel is important, but not necessarily a life or death scenario like other stuff is.