(CNN) -- A British mountaineer who recently died on Everest warned of overcrowding at the summit in his last post to social media.
Robin Haynes Fisher died of what appeared to be altitude sickness at 8,600 meters (28,215 feet), while descending from the summit on Saturday, May 25.
"I am hopeful to avoid the crowds on summit day and it seems like a number of teams are pushing to summit on the 21st," he wrote in a captioned Instagram post on May 13.
"With a single route to the summit, delays caused by overcrowding could prove fatal so I am hopeful my decision to go for the 25th will mean fewer people. Unless of course everyone else plays the same waiting game."
Haynes Fisher is one of nine climbers to have died on Everest in the 2019 climbing season as conditions on the world's highest mountain turned lethal.
During the week beginning May 20, crowds of climbers became stuck in a queue to the summit, above the mountain's highest camp at 8,000 meters (26,247 feet).
The summit of Mount Everest is 8,848 meters (29,029 feet) high, an elevation at which each breath contains only one-third of the oxygen found at sea level.
Most people can only spend a matter of minutes at the summit without extra oxygen supplies, and the area where the climbers were queuing is known as the "death zone."
Nepali climbing guide Dhruba Bista fell ill on the mountain and was transported by helicopter to the base camp, where he died Friday.
And Irish climber Kevin Hynes, 56, died Friday morning on the Tibetan side of Everest in his tent at 7,000 meters (22,966 feet).
Two died Wednesday after descending from the summit: Indian climber Anjali Kulkarni, 55, and American climber Donald Lynn Cash, 55.
Kalpana Das, 49, and Nihal Bagwan, 27, both from India, also died on Everest this week. Both died Thursday on their return from the summit.
Ravi, a 28-year-old Indian climber who goes by one name, died the previous week on May 17.
Last week, a search for Irish climber Seamus Lawless, 39, was called off, after the Trinity College Dublin professor fell while descending from the peak, according to the Press Assocation.
Lawless is missing, presumed dead.
The death toll for Everest's 2019 climbing season is not unusual for the mountain. In 2018, five climbers died, while six died in both 2017 and 2016.
More than 200 mountaineers have died on the peak since 1922, when the first climbers' deaths on Everest were recorded. The majority of bodies are believed to have remained buried under glaciers or snow.
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