Oregon-based Columbia Helicopters says it still wants to sell itself to a Texas company, even though the buyer’s share price has plunged by more than two-thirds since announcing the $559 million deal.

Bristow Group’s investors began unloading shares almost as soon as the company announced its plan to buy privately held Columbia last November, driving Bristow’s stock down from $10.04 to just $3.16.

Bristow’s deteriorating position on Wall Street has produced calls for the Texas company to scuttle the deal. But Columbia Helicopters insists it intends to sell.

“There’s a lot of talk, obviously, but the facts are the facts. There’s an agreement,” said Santiago Crespo, Columbia’s vice president of business development and strategy.

Most of the purchase price, $492 million, is to be paid in cash, much of which Bristow intends to borrow. So the precipitous decline in Bristow stock has only diminished what Columbia’s owners would receive by $43 million, about 8 percent.

It has devastated Bristow, though. The deal currently values Columbia at $516 million, 4.5 times Bristow’s diminished market capitalization.

Bristow did not respond to messages Tuesday seeking comment on the deal’s status.

Columbia Helicopters was founded in 1957 and the family of its late founder, Wes Lematta, still owns the business. When it announced the deal in November, Columbia said it would continue to be run from its existing headquarters in Aurora after Bristow takes over.

Columbia says its sales totaled $281 million in the 12 months ended in September; it did not disclose profitability. Bristow’s sales totaled $1.4 billion in its last fiscal year, which ended in March. The Texas company lost $196 million in that period.

When they announced the deal in November, the two companies said Columbia’s operations in defense, firefighting and natural resource exploration would complement Bristow’s focus on offshore oil exploration and search-and-rescue aircraft. They said that would create a stronger, more diversified company.

Investors aren’t buying it.

A Wisconsin firm called Global Value Investment Corp., which owns less than 5 percent of Bristow’s stock, sent a letter to the Texas company last week denouncing the deal for Columbia. Global Value said $360 million in debt coupled with newly issued stock to finance the acquisition is too expensive to existing shareholders.

If the deal does come apart, the sale agreement requires Bristow to pay a $20 million termination fee. But Crespo said the companies are trying to move forward together.

“We know both parties are working hard to meet the obligations of the agreement,” he said.

Oregonian reporter Jeff Manning contributed to this article.

-- Mike Rogoway | twitter: @rogoway | 503-294-7699