I-539&I-539A delivered 4days before I-94 expiry

[Ruhi3]

Hi , My parents are here on B2 Visa and their I-94 is valid till 17Sep20, however their flight got cancelled and I have applied for extension . I539 & I539 A were mailed to USCIS and it was delivered on 12Sep (Saturday). I have attached all required documents and their return tickets too, will there be any issue with them staying before receiving receipt notice from USCIS? Thanks you in advance!

[Rizwanaalavi]

As long as they receive it before your I-94 expiration date, you are good to go.