For a 42-year-old pilot, when will a Second-Class Medical Certificate issued on July 15 expire?

A Second-Class Medical Certificate for a pilot who is under 50 years of age expires 24 months from the date of issuance, provided that the pilot's age is taken into account. Since the pilot in this scenario is 42 years old, the certificate is valid for the full two years.

The certificate was issued on July 15; hence, it will remain valid until July 14 of the second year. However, the expiration is measured until the end of the final day before the two-year mark, which would be at midnight on July 31, two years later. This means that the pilot must renew the certificate before it expires on that date.

In summary, the correct answer indicates the correct date of expiration according to FAA regulations for a Second-Class Medical Certificate issued to a pilot of this age.