UPDATE 2-Inmarsat Q3 EBITDA up 18.4 pct; shares higher

* Q3 revenue $176.7 mln, EBIDTA up 18.4 pct to $133 mln

* Says on track for year

* Completes $500 mln refinancing

* Shares up 4.6 pct at more than four-year high

(Adds shares, analyst reaction)

By Paul Sandle

LONDON, Nov 9 (Reuters) - British satellite communications firm Inmarsat (ISA.L) posted a better-than-expected 18.4 percent rise in third-quarter earnings on Monday, and said it was on track for the year, sending its shares to a four-year high.

The company, whose satellites provide phone and broadband services to ships, aircraft and remote locations worldwide, posted earnings before interest, tax, depreciation and amortisation (EBITDA) of $133 million, helped by cost controls.

Revenue in the three months to end-September rose 8.7 percent to $176.7 million, the firm said, reflecting strong demand in the aeronautical sector and maritime broadband services.