In interviews this past week, leaders of the International Civil Aviation Organization, a U.N. agency that sets nonbinding safety standards for carriers and regulators, said they have had only limited success over the years in their push for enhanced oversight.

Roughly one-third of commercial-plane crashes in Asia between 2008 and 2012 to some extent “involved deficiencies in regulatory oversight,” according to a report released as part of a global ICAO safety summit held this week in Montreal.

Budget constraints, limited technical expertise and nagging personnel shortages have hampered government safety initiatives in many parts of Asia experiencing growing traffic, including Indonesia, India, Malaysia, Vietnam and Thailand, according to safety experts who aren’t affiliated with ICAO. In some instances, they said, the sheer pace of growth makes it difficult for airlines and regulators to react quickly to changes without major investments.

But the biggest potential hazards may come from less-populous countries with smaller travel markets, according to Ms. Graham. Among the countries she worries about most are Cambodia and Nepal, she said, partly because expanding tourism means “they have to have a national plan to keep their safety capabilities in front of their demand.”