The P.11 featured an internal fuel tank positioned inside the fuselage that could be jettisoned in case of fire or other emergency. A high-profile flaw was present in the construction of early-built examples in the form of its fuel tanks. Originally manufactured by an independent sub-contractor, the tanks were rivetted and covered with a resin sealing agent; however, this technique would result in joints that would rapidly degrade in the presence of vibration. An initial effort to switch to welded joints was catastrophic, having been determined to have been responsible for failures early on in the P.11's service life. Following a decision by some customers to refuse acceptance of completed aircraft using this type of joint due to these failures, extensive testing to evaluate alternative techniques was conducted by PZL, resulting in the problem being entirely eliminated.