"Khloe is very concerned but doesn't know what else she can do at this point," a source close to Kardashian tells ET.
Khloe Kardashian is clearly feeling heartbroken over a report that her ex, Lamar Odom, is still struggling with alcohol issues.
The 32-year-old reality star tweeted a sad face emoji on Tuesday, and responded to fans who alluded to a report that Odom allegedly had to be removed from a plane on Monday night. According to TMZ, Odom, 36, was taken off a Delta flight bound for New York City because he was drunk and repeatedly vomiting.
A source close to Kardashian tells ET that she and Odom are no longer speaking consistently.
"Khloe is very concerned but doesn't know what else she can do at this point," the source says. "She's tried everything she can to help him. The man was on his deathbed and she helped him get a second chance at life. If that didn’t wake him up, what will?"
WATCH: EXCLUSIVE -- Lamar Odom Opens Up About Khloe Kardashian Divorce -- 'We've Been Through a Lot'
On Tuesday, Kardashian responded to fans' messages of support.
"Can't save every soul," one Twitter user, to which Kardashian replied, "but we like to try."
She also thanked fans for their kind words.
"You gave him your hand, he didn’t take it. Stay strong, you are our role model," one user wrote, to which she replied, "Thank you sweetheart. I love you."
"You can only do so much Khlo, just pray," another fan commented, to which Kardashian responded, "amen."
"Just pray," she later tweeted in response to a comment reading, "It's out of your hands Khlo."
But it wasn't all positive. Kardashian got feisty with one user who criticized her for her reported fling with singer Trey Songz earlier this month.
"Instead of running the streets with Mr.!steal your girl you need to be helping your HUSBAND," the user wrote, to which Kardashian fired back, "Stay in your f**king lane little girl. You know nothing about anything. You're a sheep herded by society."
Los Angeles International Airport police did not respond to the reported incident involving Odom, and have no information. ET also reached out to Delta Air Lines, who declined to comment, citing customer privacy.
Kardashian filed for divorce from Odom for the second time on May 26, after initially calling off their divorce in order to make medical decisions for the former NBA star. Odom officially responded last Friday, citing irreconcilable differences in his own filing. Odom is not requesting spousal support, but did request that a judge terminate Kardashian's right to ask for alimony.
Kardashian supported Odom through his recovery after he was found unresponsive in a room at the Love Ranch brothel in Crystal, Nevada, last October due to a drug overdose, though their relationship has hit rough patches since then. In March, a source close to Kardashian told ET that she was "shocked" when Odom was spotted at a bar in Sherman Oaks, California, reportedly ordering alcohol.
"He almost died -- if that's not enough to keep him sober, then what is?" the source told ET at the time. "If Lamar makes this a habit, Khloe will walk away for good this time. Khloe is shocked that he was caught drinking again."
Another source at the time also told ET that Odom "should not be consuming any alcohol right now, and was told that by his medical team."
But on Mother's Day, Odom was again photographed sipping liquor at the Beverly Center mall in Los Angeles. "Hummmmmm... People disappoint," Kardashian tweeted shortly after the pictures were published.
WATCH: Lamar Odom Helps Rob and Khloe Kardashian Reconcile on 'KUWTK': 'Time Goes By So Fast'
On last Sunday's episode of Keeping Up With the Kardashians, the estranged couple appeared on good terms, and discussed Rob Kardashian's engagement to Blac Chyna. Lamar warned, "Marriage ain't easy, honey child."
"I been there before," he added.
Watch below: