Exhaustion of FMLA protected leave is a common problem in the Postal Service. This legal article makes several good points about ADA considerations:
The broadened scope of the ADA increases the likelihood that anyone taking FMLA leave for their own serious health condition may also have an ADA protected disability. As a result, it is important for employers to consider whether the employee is covered by the ADA (or state disability law) before separating an employee who has provided notice of his or her inability to return to work following exhaustion of the employee’s maximum FMLA leave entitlement. Oftentimes, such employee notice includes a request for additional leave and/or a doctor’s note with a return-to-work date beyond the FMLA leave expiration date. While there is no duty under the FMLA to grant additional leave, if the employee’s medical condition meets the definition of an ADA disability, there may be a duty under the ADA to consider granting additional unpaid time off from work, as some courts have held that leave is a form of reasonable accommodation.