Flying into Chisinau Airport is typically the best way to visit Kishinev Cathedral, since it is the closest airport to the area.
If you are looking to fly to Moldova for less, look to airlines like Wizz Air, TAROM, and Wizz Air UK, with prices starting at $49, $91, and $93 respectively.
Moldova has restricted entry to most foreign travelers until at least September 15. Until September 15, Moldova's border only permits foreigners if they meet one of the following exceptions: immediate family members of Moldovan citizens; persons having a visa, residency permit, or other document issued by Moldovan authorities; persons traveling for "professional interest" in possession of a visa, residency permit, or other document issued by Moldovan authorities; diplomats accredited to Moldova and members of international organizations and their family members; personnel who can provide humanitarian aid; passengers in transit. As of June 30, other categories of people are allowed to enter Moldova. These include: people with a business visit visa, long-stay visa, residence permit or equivalent document, members and dependents of diplomatic missions, consular Posts and international organizations accredited in Moldova, personnel providing humanitarian aid, passengers in transit, people traveling for health and humanitarian reasons, cross-border workers, and drivers and service personnel, for the purpose of transportation of goods (aircraft, ship and train crew). PCR and/or serology is not required to enter Moldova but all travelers must complete an epidemiological questionnaire ("fisa epidemiologica") at airports and other ports of entry when entering Moldova and sign a statement that they will self-isolate for 14 days. Starting September 1, Moldova requires a 14-day home stay (quarantine) for new arrivals from certain countries, with exceptions including asymptomatic individuals delivering goods, crew members, students, people traveling for health care, work related travelers with visas, diplomatic corps accredited in Moldova, and passengers in transit. See this website for the list of countries on the “red” list which require the quarantine. The list will be updated every two weeks. If you are planning to travel to Moldova at this time, it is recommended that you stay up to date on current restrictions and follow proper safety measures while in public.