Before Harris spoke in church, Biden were surveying hurricane damaged over a helicopter flight between Tampa and St. Pete Beach on the Gulf Coast.

The original phrase "Biden were surveying hurricane damaged" contains two errors. First, "were" should be "was" to agree with the singular subject "Biden." Second, "hurricane damaged" should be corrected to "hurricane damage," which accurately describes the destruction caused by the hurricane. The preposition "on" is also the correct choice for indicating the type of flight. Thus, the corrected sentence would read: "Before Harris spoke in church, Biden was surveying hurricane damage on a helicopter flight between Tampa and St. Pete Beach on the Gulf Coast."