Qt4 is dead and going away.
https://github.com/bistromath/gr-air-modes/blob/master/apps/modes_gui Looks like it uses qt4. You could just disable GUI support if you want to kill qt4 in the tree.
In fact, this package is broken already since it missed to depend on PyQt4[qtwebkit] which is gone for a long time.
The bug has been closed via the following commit(s):
Author: Andreas Sturmlechner <email@example.com>
AuthorDate: 2018-03-04 12:17:10 +0000
Commit: Andreas Sturmlechner <firstname.lastname@example.org>
CommitDate: 2018-03-04 12:38:10 +0000
net-wireless/gr-air-modes: Drop broken USE=gui
Package-Manager: Portage-2.3.24, Repoman-2.3.6
net-wireless/gr-air-modes/gr-air-modes-9999.ebuild | 5 ++---
net-wireless/gr-air-modes/metadata.xml | 1 -
2 files changed, 2 insertions(+), 4 deletions(-)