It's convenient to think of Honolulu International Airport as simply a place to catch a flight. But the airport is also a business; it needs to efficiently attract customers to remain competitive.

It's a tough task, and it's become increasingly difficult in recent years. The overall increase in the number of travelers and flights, coupled with the demands of post-9/11 security systems, have created conditions that make travelers grit their teeth: endless check-in lines, relentlessly invasive security checks, and dingy, uncomfortable waiting areas.

Add rising airfares, a weak economy and fewer flight options to the mix and it's enough to make travelers think twice about leaving home. For a tourist-based economy such as Hawai'i's, that's bad news.

But it's also one reason the state should proceed with its $2.3 billion upgrade of five Hawai'i airports. It's a wise long-term investment in our economy, even if the short-term outlook seems bleak.

Aloha and ATA airlines won't be paying the $15 million in landing fees and rents they were expected to. Their collapse led to a 14 percent drop in visitors this month.

And the possibility of mergers among four airlines serving Honolulu could mean fewer flights and a similar loss of visitors and revenue.

Last year, Gov. Linda Lingle released $75.5 million for Hono-lulu International Airport, for improvements such as moving an in-line explosives-detection system away from check-in lines, a new parking structure and air-conditioning upgrades.

It's a good start. But the momentum mustn't lag. The Wiki Wiki bus system needs to be replaced with an efficient people mover; foreign tourists need a faster way to clear Customs; and configuration of the check-in counters needs to encourage efficiency.

Hawai'i's airports are a visitor's first and last impression of the Islands. It should be a good one — that's just good business.