The half-life of most SSRIs is measured in hours, and at most days. Therefore they will be completely out of your system in days / weeks.
In the UK, the CAA requires a period of at least 3 months between ceasing anti-depressants and restoration / granting of a medical certificate.
Good luck with ceasing the SSRI - these things are known to provoke quite nasty withdrawal symptoms, depending on the individual, the specific drugs & dosage and the rate of cessation.
SD